Method and system for adaptively obtaining bandwidth allocation requests

ABSTRACT

A method and apparatus for adaptively obtaining bandwidth requests in a broadband wireless communication system. The method and apparatus includes dynamically varying technique combinations enabling a plurality of users to efficiently request bandwidth from a shared base station. A user may “piggyback” a new bandwidth request upon, or set a “poll-me bit” within, presently allocated bandwidth. A base station may poll users, individually or in groups, by allocating unrequested bandwidth for new requests. Polling may respond to a “poll-me bit,” and/or it may be adaptively periodic at a rate based on communication status parameters, such as recent communication activity and connection QoS levels Group polling permits a possibility of collisions. Polling policies may be established for dynamically varying user groups, or may be determined for each user. Dynamic selection of appropriate polling techniques makes use of efficiency benefits associated with each technique.

RELATED APPLICATIONS

This application is a continuation of application Ser. No. 12/370,506,filed Feb. 12, 2009, which is a continuation of application Ser. No.11/350,474, filed Feb. 8, 2006, (now U.S. Pat. No. 7,751,437), which isa continuation of application Ser. No. 10/014,951, filed Dec. 11, 2001(now U.S. Pat. No. 7,006,530), which claims the benefit of U.S.provisional application No. 60/257,525, filed Dec. 22, 2000, all ofwhich are hereby incorporated by reference. This application is also acontinuation-in-part of application Ser. No. 11/170,392, filed Jun. 29,2005, which is a continuation of application Ser. No. 09/859,561, filedMay 16, 2001 (now U.S. Pat. No. 6,956,834), which is a continuation ofapplication Ser. No. 09/316,518, filed May 21, 1999 (now U.S. Pat. No.6,925,068), all of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to wireless communication systems and toefficiently allocating bandwidth between base stations and users in awireless communication system.

2. Description of Related Art

Recently, wideband or “broadband” wireless communications networks havebeen proposed for providing delivery of enhanced services such as voice,data and video services. The broadband wireless communication systemfacilitates two-way communication between a base station and a pluralityof fixed subscriber stations or Customer Premises Equipment (CPE)stations. One exemplary broadband wireless communication system isdescribed in related U.S. Pat. No. 6,016,311, and shown in block diagramof FIG. 1.

As described in related U.S. Pat. No. 6,016,311, which is herebyincorporated by reference, a wireless communication system facilitatestwo-way communication between a plurality of subscriber radio stationsor subscriber units (fixed or portable) and a fixed networkinfrastructure. Exemplary communication systems include mobile cellulartelephone systems, personal communication systems (PCS), and cordlesstelephones. A key objective of these wireless communication systems isto provide communication channels on demand between a plurality of userunits and one or more associated base stations in order to connect asubscriber or user with a network infrastructure (such as the Internet).Both wired and wireless systems, however, may have multiple accessschemes which permit a particular user to obtain access to sharedcommunication media, such as a particular physical radio channel. Manyof such shared media systems divide access between various users byallocating timeslots within a time “frame,” which is used as a basicinformation transmission unit. Each frame is typically sub-divided intoa plurality of time slots, which may be synchronous or asynchronouswithin the frame, some of which are used for control purposes and somefor information transfer.

Bidirectional communication units typically use a “duplexing” scheme toallow information flow in both directions. Transmissions from the basestation to users are commonly referred to as “downlink” transmissions.Transmissions from a user to the base station are commonly referred toas “uplink” transmissions. Time division duplexing (TDD) and frequencydivision duplexing (FDD) methods are examples of duplexing schemes tofacilitate the exchange of information in both directions between basestations and users.

As shown in FIG. 1, the exemplary broadband wireless communicationsystem 100 includes a plurality of cells 102. Each cell 102 contains anassociated cell site 104 that primarily includes a base station 106 andan active antenna array 108. Each cell 102 provides wirelessconnectivity between the cell's base station 106 and a plurality ofcustomer premises equipment (CPE) 110 positioned at fixed customer sites112 throughout the coverage area of the cell 102. The users of thesystem 100 may include both residential and business customers. Eachcell may service several hundred or more residential and business users.

The type and quality of services available to the customers are variableand selectable. Different broadband services have different bandwidthand latency requirements, depending on the information rate and thequality of service they provide. For example, T1-type continuous bitrate (CBR) services typically require bandwidth sufficient tocommunicate at a well-defined data rate which has well-controlleddelivery latency. Until terminated, these services generally requirebandwidth allocation at a constant rate. In contrast, certain othertypes of data services, such as Internet protocol data services, arebursty, frequently idle (momentarily requiring zero bandwidth), and arerelatively insensitive to delay variations when active.

Due to the wide variety of user service requirements, and due to thelarge number of users serviced by any one base station, the bandwidthallocation process in a broadband wireless communication system such asthat shown in FIG. 1 can become burdensome and complex. This isespecially true with regard to the allocation of uplink bandwidth. Basestations do not have a priori information regarding the bandwidth orquality of services that a selected user will require at any given time.Consequently, requests for changes to the uplink bandwidth allocationare necessarily frequent and varying. Due to this volatility in theuplink bandwidth requirements, the many CPEs serviced by a selected basestation will frequently need to request bandwidth allocation. Ifuncontrolled, the bandwidth allocation requests will detrimentallyaffect system performance. The bandwidth required to accommodate userbandwidth allocation requests can become disproportionately high incomparison with the bandwidth allocated for the transmission ofsubstantive data traffic, reducing the communication system bandwidthavailable to provide broadband services. This principle applies to mostcommunications systems which share a limited communication medium amongvarying user connections.

Therefore, a need exists for a method and apparatus that can dynamicallyand efficiently allocate bandwidth in response to varying bandwidthneeds in a shared media communication system. The method and apparatusshould be responsive to the needs of a particular communication link.The bandwidth allocation method and apparatus should be efficient interms of the amount of system bandwidth consumed by the actual bandwidthrequest and allocation process. That is, the bandwidth requestsgenerated by the user should consume a minimum percentage of availableuplink bandwidth. In addition, the bandwidth allocation method andapparatus should respond to bandwidth requests in a timely manner.Bandwidth should be allocated to high priority services in asufficiently short time frame to maintain the quality of servicespecified by the user. Further, the bandwidth allocation method andapparatus should be capable of processing an arbitrarily large number ofbandwidth allocation requests from a relatively large number of users.For example, in the system shown in FIG. 1, over one hundred users maybe allowed to be simultaneously active, coordinating their transmissionson the uplink. The exemplary system can accommodate approximately onethousand CPEs on the physical channel.

Some prior art systems have attempted to solve bandwidth allocationrequirements in a system having a shared system resource by maintaininglogical queues associated with the various data sources requiring accessto the shared system resource. Such a prior art system is taught byKarol et al., in U.S. Pat. No. 5,675,573, that issued on Oct. 7, 1997.More specifically, Karol et al. teach a bandwidth allocation system thatallows packets or cells within traffic flows from different sources thatare contending for access to a shared processing fabric to get access tothat fabric in an order that is determined primarily on individualguaranteed bandwidth requirements associated with each traffic flow. Inaddition, the system taught by Karol et al. allows the different sourcesto gain access to the shared processing fabric in an order determinedsecondarily on overall system criteria, such as a time of arrival, ordue date of packets or cells within the traffic flows. Packets or cellsof data from each data source (such as a bandwidth requesting device)are queued in separate logical buffers while they await access to theprocessing fabric.

A need exists for efficient bandwidth allocation methods whichaccommodate an arbitrarily large number of users having uplink bandwidthneeds which vary frequently. The inventors have recognized that in orderto efficiently allocate bandwidth, it is important to determine thebandwidth needs of users in a timely, accurate and efficient manner.

SUMMARY OF THE INVENTION

In response to the above-identified need, a method and apparatus ispresented herein for adaptively obtaining requests for bandwidthallocation in a shared media communication system. Adaptively obtainingbandwidth requests reduces the amount of bandwidth that is consumed forbandwidth request purposes, and provides the communication system withthe information needed to efficiently allocate bandwidth for each userwithin the capacity limits of the system. Since some techniques forobtaining bandwidth requests require allocating bandwidth to the usersfor the purpose of requesting bandwidth, varying combinations of anumber of bandwidth request and allocation techniques may be adaptivelyemployed to efficiently determine and respond to changing user bandwidthneeds. Each user, or group of users, is evaluated on one or moreselected communications parameters, and the particular technique forobtaining bandwidth requests, or the rate of application of thattechnique, is selected or changed for the user or user group in responseto changes in the selected communications parameters associated with theuser or user group.

There are a number of techniques by which base stations can obtainbandwidth request messages from associated users. One such technique is“polling,” whereby a base station polls one or more users by allocatingbandwidth to the users specifically for the purpose of allowing theusers to respond with a bandwidth request. Polling may be directedexclusively to a particular user (individual polling), or to a group ofusers (multicast or broadcast polling). Such polling of the users by thebase station may be in response to a user setting a “poll-me” message,or it may be periodic without prompting from the user, or it may beperformed in response to aperiodic conditions.

When an alternative means to obtain bandwidth requests is available, thebandwidth consumed for obtaining bandwidth requests may be reduced byallowing the periodic polling rate for a particular user or group to goto zero. For example, if uplink bandwidth is already allocated to aparticular user or group then mechanisms such as setting a “poll-me”marker to explicitly request to be polled, or “piggybacking” bandwidthrequests on existing bandwidth, may provide sufficient opportunity torequest any needed bandwidth allocations. These techniques are usefulfor currently active users and groups, and such active users and groupsmay accordingly require zero periodic polling until their activity leveldeclines.

Adaptation in obtaining bandwidth requests is performed on the basis ofchanging communication parameters, and may occur on different levels.First, users may be adaptively moved between different techniques forobtaining bandwidth (e.g., periodic individual polls, requestedindividual polls, multicast polls, and piggybacking). Second, rates ofperiodic individual or multicast polling, or conditions for respondingto requests for polling, may be dynamically adapted for each user orgroup of users.

The changing communication parameters upon which adaptation is based mayinclude parameters associated with a particular user or group, such asthe quality of service (QoS) required by user connections, the rate ofrecent bandwidth usage associated with the user or group, and a prioritycontractually negotiated for the user or group. Parameters associatedwith the overall system may also be used, such as the amount ofbandwidth available for sharing, the composite number of users and theiractivity levels, and the composite priority and expected quantity ofother bandwidth requests.

A particular base station may be configured to treat any or all ofdiscrete connections, groups of connections, CPEs, or other logical orphysical entities, as distinct users. Each user's polling rate ortechnique is typically dynamically adaptive, based on one or moreparameters of the user and/or of the system. Parameters may bedetermined and maintained as values which are continuously variablewithin the quantization constraints of the constituent components of theparameters. Alternatively, parameters may be categorized, and thusdetermined or maintained as merely one of a finite or limited number ofcategorical values. These parameter values are in turn used to determinea polling rate and/or technique to apply to each user. Polling rates maythemselves be determined as continuously as the values on which they arebased allow, or may be further quantized into a smaller number of ratecategories. Rates and techniques may be determined for each user entity,or may be determined for groups of users. Thus, the process ofadaptively obtaining bandwidth requests may be based on groupings,categories and quantization of both users and of various system and usercommunication parameters. Such flexibility permits a wide range ofdifferent systems to employ various embodiments of the invention taughtherein to improve the efficiency and effectiveness of their bandwidthallocation process.

Users may be grouped with other users in a “polling group” to whichindividual users are dynamically assigned based upon factors such as thephysical proximity of the users to a base station, or a modulation leveland forward error correction which is provided to them. Groups ofindividual connection users may be distinguished on the basis of factorssuch as the CPE through which the connection is maintained, the QoSrequirements of the connections, or on load sharing considerationswithin a CPE or a base station.

When a user or group has low usage, sufficient bandwidth requestopportunities to meet the guaranteed quality of service may in somecases be provided by periodically multicast polling the user or group,despite the statistical possibility of a collision entailed by suchmulticast polling. A contention resolution process is useful inconjunction with such multicast polling. The rate of multicast pollingwhich is sufficient for a user or group depends upon the quality ofservice guaranteed to the user or group, in combination with thestatistical probability of a collision and the time delay which would beintroduced by a collision. The rate of “contention” polling maytherefore be adaptively adjusted in response to changes in parameterssuch as the guaranteed quality of service, the number of userssimultaneously polled, the history of previous use, and other factorssuggesting a probability of activity.

To reduce the bandwidth absorbed by the process of obtaining bandwidthrequests, the foregoing and other methods for obtaining bandwidthrequests are used adaptively, dynamically changing the technique used toobtain bandwidth requests in accordance with the prevailing conditionsand communication parameters for each user or group.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a broadband wireless communication system.

FIG. 2 shows a TDD frame and multi-frame structure that can be used bythe communication system of FIG. 1.

FIG. 3 shows a downlink sub-frame that can be used by a base station totransmit information to the plurality of CPEs in the wirelesscommunication of FIG. 1.

FIG. 4 shows an exemplary uplink sub-frame.

FIG. 5 is a flow diagram showing the information exchange sequence usedin practicing some individual polling techniques.

FIG. 6 is a flow diagram showing an individual polling technique.

FIG. 7 shows an exemplary uplink sub-frame map for multicast/broadcastpolling.

FIG. 8 is a flow diagram showing a multicast and broadcast pollingtechnique.

FIG. 9 is a flow diagram showing use of a “poll-me” message to stimulatepolling.

FIG. 10 shows a message sequence for requesting polls using a “poll-me”bit.

FIG. 11 is a flow diagram showing a bandwidth request piggybackingprocess.

FIG. 12 shows a downlink bandwidth allocation method.

FIG. 13 shows an uplink bandwidth allocation method.

FIG. 14 is a flowchart for an adaptive polling group assignment methodor system.

FIG. 15 is a flowchart for adaptively obtaining bandwidth requests foreach user.

FIG. 16 is a chart of polling policy control information flow betweensystem modules.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION OF THE INVENTION

Throughout this description, the embodiments and examples shown shouldbe considered as exemplars, rather than as limitations on the presentinvention.

A method and apparatus for adaptively obtaining bandwidth requests in aDemand Assigned Multiple Access (DAMA) communication system is describedherein. One very important performance criterion of a communicationsystem having a physical communication medium shared by a plurality ofusers is how efficiently the system uses the physical medium. Since manywireless communication systems are shared-medium communication networks,access and transmission by subscribers within such networks must becontrolled. In such communication systems, a Media Access Control(“MAC”) protocol typically controls user accesses to the physicalmedium. The MAC determines when subscribers are allowed to transmit onthe physical medium. In addition, if contentions are permitted, the MACcontrols the contention process and resolves any collisions that occur.In a Demand Assigned Multiple Access (DAMA) system, which grants accessto a shared media on an as-requested basis, a MAC may be designed toadaptively vary the method by which requests for access, or bandwidth,are obtained so as to efficiently determine and respond to bandwidthneeds to assure a requisite quality of service (QoS), without wastingbandwidth by unnecessarily polling for such requests.

In the exemplary system shown in FIG. 1, the MAC (executed by softwareand/or hardware present in the base stations 106 or in both the basestations and the CPEs 110) controls the transmission time for all of theCPEs 110. The base stations 106 receive requests for transmissionrights, and may grant these requests in accordance with parametersassociated with each CPE 110, such as priorities, service types, QoS,and recent usage level, and also in accordance with system parameterssuch as available bandwidth and competing requests for transmissionrights. The services provided by the CPEs 110 may include constantbit-rate TDM information connections, such as voice trunks from a PBX,requiring a high QoS. At the other end of the service spectrum, the CPEsmay communicate bursty but delay-tolerant computer data to other datadevices via networks such as the Internet.

The base station MAC maps and allocates bandwidth for both the uplinkand downlink communication links. These maps are developed andmaintained by the base station and are referred to as the UplinkSub-frame Maps and Downlink Sub-frame Maps. The MAC must allocatesufficient bandwidth to accommodate the bandwidth requirements imposedby high priority constant bit rate (CBR) services such as T1, E1 andsimilar constant bit rate services. In addition, the MAC must allocatethe remaining system bandwidth across the lower priority services suchas Internet Protocol (IP) data services. The MAC distributes bandwidthamong these lower priority services using various techniques which maybe dependent on QoS, such as fair-weighted queuing and round-robinqueuing.

The downlink of the exemplary communication system shown in FIG. 1operates on a point-to-multi-point basis (i.e., from the base station106 to the plurality of CPEs 110). As described in U.S. Pat. No.6,016,311, the central base station 106 includes a sectored activeantenna array 108 which is capable of simultaneously transmitting toseveral sectors. In one embodiment of the system 100, the active antennaarray 108 transmits to six independent sectors simultaneously. Within agiven frequency channel and antenna sector, all stations receive thesame transmission. The base station is the only transmitter operating inthe downlink direction, hence it transmits without having to coordinatewith other base stations. In the case of TDD, the base station mustcoordinate downlink transmission with uplink reception time; of course,in FDD systems this constraint does not exist, and the uplink anddownlink transmissions are instead segregated by transmission carrierfrequency. The base station broadcasts to all of the CPEs in a sector.The CPEs monitor the addresses in the received messages and retain onlythose messages addressed to them.

It will be understood by those skilled in the art, without furtherspecific mention, that both the CPEs and the base stations may performthe tasks ascribed to them using a combination of hardware, firmware andsoftware control. Engineering considerations drive the allocation offunctions to software, firmware and/or hardware. In particular, both theCPEs and the base stations will generally employ a computer running asoftware program which performs the ascribed functions, or directshardware to perform the ascribed tasks in functional modules preparedfor such tasks. At least some of the physical communication must beperformed in hardware, but data manipulations may be performed by acomputer operating under software control, or by microprocessorsoperating under firmware control, or by ASICs, a portion of which isused for the specific data manipulations which are required.

The CPEs 110 share the uplink on a demand basis that is controlled bythe base station MAC. Depending upon the class of service utilized by aCPE, the base station may issue continuing rights to a selected CPE totransmit on the uplink, or the right to transmit may be granted by abase station after receipt of a request from the CPE. In addition toindividually addressed messages, messages may also be sent by the basestation to multicast groups (control messages and video distribution areexamples of multicast applications) as well as broadcast to all CPEs.

Decisions regarding bandwidth request and allocation techniques aretypically made for a particular sector and channel, since this is thebasic communication media which must be shared and allocated.

Frame Maps—Uplink and Downlink Sub-Frame Mappings

The base stations 106 may maintain maps of the bandwidth allocated tothe uplink and downlink communication links. Uplink and downlink may beduplexed in any convenient manner, such as time-division duplexing (TDD)or frequency-division duplexing (FDD). A frame may be defined as acommunication media subunit, and typically has a predictable duration.It may comprise N consecutive time periods or time slots, or may beorganized in sections of continuously variable length. In Adaptive TimeDivision Duplexing (ATDD), the communication system dynamicallyconfigures the first period, T₁, or the first N₁ time slots (where N₁ isless than or equal to N) for downlink transmissions only, while theremaining frame period time T₂ or the remaining N₂ time slots aredynamically configured for uplink transmissions only (where N₂ equalsN−N₁). Under this ATDD frame-based scheme, the downlink sub-frame istypically transmitted first and is prefixed with information that isnecessary for frame synchronization. In FDD, uplink and downlinkchannels on different frequencies may each be divided into N time slotsto form an uplink sub-frame or a downlink sub-frame. Time divisionmultiple access (TDMA) techniques may be used to multiplex use of theuplink and downlink channels in such a framed system, as detailed below,but the skilled person will appreciate that framing is not essential forthe dynamic, adaptive techniques taught herein for allocating bandwidthand obtaining bandwidth requests. In non-framed systems one maydynamically vary (in response to varying conditions) a schedulinginterval for submitting bandwidth requests.

FIG. 2 shows an ATDD frame and multi-frame structure 200 that can beused by a communication system such as that shown in FIG. 1. As shown inFIG. 2, the ATDD frame is subdivided into a plurality of physical slots(PS) 204. In the embodiment shown in FIG. 2, the frame may, for example,be one millisecond in duration and include 800 physical slots. The framelength and the number of PS in a frame are widely variable dependingupon engineering considerations; the number of PS can be reduced orincreased as far as the limits of system time resolution, andembodiments with no frame structure are possible, as long as a physicalcommunication medium is shared and users are granted bandwidth ondemand. In an exemplary embodiment, the available bandwidth is allocatedby a base station in units of a certain pre-defined number of PSs.

Some form of digital encoding, such as the well-known Reed-Solomonencoding method, is typically performed on the digital information overa pre-defined number of bit units referred to as protocol informationelements (PI). Since the data rate varies according to the modulationscheme employed, the modulation scheme controls the amount of time(i.e., number of PSs) required to transmit each PI—in an exemplaryembodiment, a PI requires 6 PSs at QAM-4 modulation.

The uplink and downlink time division shown in FIG. 2 is adaptive, sothat a division 210 between an uplink subframe 212 and a downlinksubframe 214 moves, as indicated, toward one end or other of the frame216 to adjust the proportions of uplink and downlink bandwidth in theframe. Thus, in a framed ATDD protocol, the number of PSs allocated tothe downlink versus the uplink varies over time. As shown in FIG. 2, toaid periodic functions, multiple frames 202 are grouped intomulti-frames 206, and multiple multi-frames 206 are grouped intohyper-frames 208. In one embodiment, each multi-frame 206 comprises twoframes 202, and each hyper-frame comprises twenty-two multi-frames 206.Other frame, multi-frame and hyper-frame structures can be used. Forexample, in another embodiment, each multi-frame 206 comprises sixteenframes 202, and each hyper-frame comprises thirty-two multi-frames 206.The present method and apparatus for adaptively obtaining bandwidthrequests can be used in frame and multi-frame structures similar to thatshown in FIG. 2, whether ATDD or fixed TDD, and applies equally well toother framed and unframed TDMA systems, including FDD systems in whichthe uplink and downlink subframes do not share a hyperframe 208 witheach other, but are segregated from each other on different carrierfrequencies.

Exemplary downlink and uplink sub-frames which may be used are shownrespectively in FIGS. 3 and 4. Note that these sub-frame structures areequally applicable irrespective of whether the duplexing scheme is TDDor FDD.

Downlink Sub-Frame Map

FIG. 3 shows one example of a downlink sub-frame 300 that can be used bythe base stations 106 to transmit information to the plurality of CPEs110. The base station may maintain a downlink sub-frame map thatreflects the downlink bandwidth allocation. The downlink sub-frame 300may comprise a frame control header 302, a plurality of downlink dataPSs 304 grouped by modulation type (e.g., PS 304 data modulated using aQAM-4 modulation scheme, PS 304′ data modulated using QAM-16, etc.) andpossibly separated by associated modulation transition gaps (MTGs) 306used to separate differently modulated data, and a transmit/receivetransition gap 308. In any selected downlink sub-frame any one or moreof the differently modulated data blocks may be absent. Modulationtransition gaps (MTGs) 306 may be 0 PS in duration. As shown in FIG. 3,the frame control header 302 contains a preamble 310 used by thephysical protocol layer (or PHY) for synchronization and equalizationpurposes. The frame control header 302 also includes control sectionsfor both the PHY (312) and the MAC (314).

The downlink data PSs are used for transmitting data and controlmessages to the CPEs 110. This data may be encoded (for example, using aReed-Solomon encoding scheme) and transmitted at the current operatingmodulation used by the selected CPE. Data may be transmitted in apre-defined modulation sequence, such as: QAM-4, followed by QAM-16,followed by QAM-64. The modulation transition gaps 306 contain preamblesand are used to separate different modulations. The PHY Control portion312 of the frame control header 302 may contain a broadcast messageindicating the identity of the PS 304 at which the modulation schemechanges. Finally, as shown in FIG. 3, the Tx/Rx transition gap 308separates the downlink sub-frame from the uplink sub-frame which isdescribed in more detail below. In an FDD system the gap 308 wouldinstead be a frame transition gap, and might be 0 PS long.

Uplink Sub-Frame Map

FIG. 4 shows one example of an uplink sub-frame 400 that is adapted foruse with the presently described bandwidth allocation. Here, the CPEs110 (FIG. 1) use the uplink sub-frame 400 to transmit information(including bandwidth requests) to their associated base stations 106. Asshown in FIG. 4, there are three main classes of MAC control messagesthat are transmitted by the CPEs 110 during the uplink frame: (1) thosethat are transmitted in contention slots reserved for CPE registration(Registration Contention Slots 402); (2) those that are transmitted incontention slots reserved for responses to multicast and broadcast pollsfor bandwidth allocation (Bandwidth Request Contention Slots 404); andthose that are transmitted in bandwidth specifically allocated toindividual CPEs (CPE Scheduled Data Slots 406).

The bandwidth allocated for contention slots (i.e., the contention slots402 and 404) may be grouped together and transmitted using apre-determined modulation scheme. For example, in the embodiment shownin FIG. 4 the contention slots 402 and 404 are transmitted using a QAM-4modulation. The remaining bandwidth is grouped by CPE. During itsscheduled bandwidth, a CPE 110 transmits with a fixed modulation that isdetermined by the effects of environmental factors on transmissionbetween that CPE 110 and its associated base station 106. The downlinksub-frame 400 includes a plurality of CPE transition gaps (CTGs) 408that serve a similar function to the modulation transition gaps (MTGs)306 described above with reference to FIG. 3. That is, the CTGs 408separate the transmissions from the various CPEs 110 during the uplinksub-frame. In one embodiment, the CTGs 408 are 2 physical slots induration. A transmitting CPE may transmit a 1 PS preamble during thesecond PS of the CTG 408, thereby allowing the base station tosynchronize to the new CPE 110. Multiple CPEs 110 may be permitted totransmit in the registration contention period simultaneously, resultingin collisions. When a collision occurs the base station may not respond.

Scheduled uplink traffic data is bandwidth allocated to specific CPEs110 for the transmission of control messages and services data. The CPEscheduled data is ordered within the uplink sub-frame 400 based upon themodulation scheme used by the CPEs 110. In the adaptive manner describedin detail below, bandwidth is requested by a CPE 110 and is subsequentlygranted by an associated base station 106. All of the bandwidthallocated to a selected CPE within a given uplink sub-frame ispreferably grouped into a contiguous CPE scheduled data block 406. Thephysical slots allocated for the CTGs 408 are included in the bandwidthallocation to a selected CPE 110 in the base station uplink sub-framemap.

In addition to the bandwidth that is allocated for the transmission ofthe various types of broadband services (i.e., the bandwidth allocatedfor the CPE scheduled data slots 406), and the bandwidth allocated forCPE registration contention slots, bandwidth must also be allocated bythe base station MAC for control messages such as requests foradditional bandwidth allocations. As described in more detail below,CPEs 110 request changes to their bandwidth allocations by makingbandwidth requests to their associated base stations 106. The presentmethod and apparatus reduces the amount of bandwidth consumed for thesebandwidth allocation requests. It is advantageous to adaptively utilizea combination of a number of techniques to tightly control the bandwidthrequest process.

Obtaining Requests for Bandwidth Allocation

There are a number of methods by which a CPE can transmit a bandwidthrequest message to its associated base station. When sufficientbandwidth is available, a CPE may transmit a bandwidth unit dedicated torequesting further bandwidth. When sufficient bandwidth for a dedicatedbandwidth request is not apparently available, a bandwidth request maybe “piggybacked” on existing bandwidth by commandeering all or part ofthe bandwidth for a request. Several methods for obtaining bandwidthrequests involve a “polling” technique whereby a base station polls oneor more CPEs and allocates bandwidth specifically for the purpose ofallowing the CPE(s) to transmit bandwidth requests. These methodsinclude: individual polling of a CPE by the base station in response tothe CPE soliciting a poll (for example, by setting a “poll-me” messagein an upstream transmission); individual polling; and “multicast”polling of groups of users. Polling individual users may be referred toas “reservation-based” polling. Individual polling may be performed “asoften as possible,” or may be performed periodically. Both individualand multicast polling may be periodic at intervals which may further bevaried dynamically with changing conditions such as current usage leveland QoS needs. Multicast polling includes the special case of broadcastpolling to every CPE on a physical channel. In reservation-basedpolling, the base station may poll an individual CPE by allocatinguplink bandwidth to allow the CPE to respond with a bandwidth request.Similarly, in multicast and broadcast polling, the base station pollsseveral CPEs by allocating uplink bandwidth to allow the several CPEs torespond with a bandwidth request. In multicast polling, the CPEs mustcontend for the allocated bandwidth if collisions occur. Advantageously,neither the bandwidth polls nor the bandwidth allocations are in theform of explicit messages that are communicated by the base station tothe CPEs. Rather, the bandwidth polls may comprise grants of bandwidthsufficient for transmitting bandwidth requests. Bandwidth allocationgrants are implicit via the bandwidth allocations indicated in theuplink sub-frame map. The polling techniques are described in moredetail below with reference to FIGS. 4-10 and 14.

As shown in FIG. 4, a portion of the uplink bandwidth may periodicallybe allocated for these bandwidth allocation or CPE connection requests.The uplink sub-frame 400 includes a plurality of bandwidth requestcontention slots 404. A CPE 110 must first be registered and achieveuplink synchronization with a base station before it is allowed torequest bandwidth allocation, and there is therefore no need to allowfor transmit time uncertainties in the length of the bandwidth requestcontention period. Consequently the bandwidth request contention periodmay be as small as a single PI, which, in one embodiment, at QAM-4requires 6 PS. As with the registration requests, if a collision occurs,the base station may not respond to the CPE. If, however, the basestation successfully receives a bandwidth request message from a CPE, itresponds by allocating the CPE additional scheduled data 406 bandwidthin the uplink sub-frame 400. Multicast polling, in which any or all ofthe CPEs so polled may respond within contention slots such ascontention slots 404, is an alternative to reservation-based pollingwhich can be efficient for low-usage CPEs. The various pollingtechniques are described in more detail below.

A method for submitting bandwidth request messages to the base stationwithout a need for polling is the technique of “piggybacking” bandwidthrequests on bandwidth which is already allocated to a CPE. In accordancewith this technique, currently active CPEs request bandwidth usingpreviously unused portions of uplink bandwidth that is already allocatedto the CPE. Alternatively, bandwidth requests are piggybacked on uplinkbandwidth allocated and actively being used by a data service. Inaccordance with this alternative, the CPE “steals” bandwidth alreadyallocated for a data connection by inserting bandwidth requests in timeslots previously intended for data. The details of these piggybackingtechniques are described in more detail below with reference to FIG. 11.

Currently active CPEs may require all of their allocated bandwidth tokeep up with high-priority communications. For this situation, analternative to piggybacking a complete bandwidth request will be useful.A place for a “poll-me” message may be reserved in a packet. Such a“poll-me” message may be a single bit, or a particular combination ofbits, and may be disposed for example as part of the header of uplinkpackets. A CPE needing all present bandwidth may simply set the“poll-me” message in an uplink packet which is already being sent inpreviously allocated bandwidth. A multiple-bit “poll-me” message may usebits which convey different control messages for other purposes at othertimes.

The various bandwidth allocation request process techniques introducedabove are described in more detail in the sub-sections that follow. Allof the techniques may be used in various combinations to reduce thebandwidth consumed obtaining bandwidth allocation requests. It isadvantageous to make use of the efficiency benefits associated with eachbandwidth allocation request technique by dynamically adapting thetechnique used with each user based upon the present conditions of theuser, the CPE if different from the user, and the channel generally. Forexample, although an individual polling technique is beneficial withregard to the ability to provide fast response times to bandwidthallocation requests, it can be relatively inefficient with regard to theamount of bandwidth consumed by the bandwidth allocation process. Incontrast, the group polling method is relatively efficient with regardto the bandwidth consumed by the bandwidth allocation process foroccasional bandwidth requests, but it is less efficient with regard tothe ability to respond to frequent bandwidth allocation requests whichcause collisions. Use of a “poll-me” bit is relatively efficient whenconsidered from both the bandwidth consumption and response timeperspectives but requires that the CPE already have uplink bandwidthallocated. Similarly, the piggybacking technique may enhance bandwidthconsumption efficiency by using previously unused portions of thebandwidth to send the bandwidth allocation requests, but this techniquerequires existing bandwidth allocation. It is advantageous to adaptivelyuse all of these bandwidth allocation techniques in variouscombinations, based on conditions such as the amount of usage byparticular CPEs and their requisite QoS, in order to maximizeefficiency.

Polling Techniques

In one embodiment of the broadband wireless system 100 of FIG. 1, a CPE110 is assigned a dedicated connection identifier (ID) when the CPE 110first registers with the system 100. The ID may be used when the basestation 106 exchanges control messages with each of the plurality ofCPEs 110. As described above, variations in bandwidth requirements(i.e., increases or decreases to bandwidth requirements) are necessaryfor all services transported by the system 100 with the exception ofuncompressible constant bit rate, or continuous grant (CG) services. Thebandwidth requirements of uncompressible CG services do not changebetween connection establishment and termination. Even the requirementsof compressible CG services, such as channelized-T1 services, mayincrease or decrease depending on traffic. Since a particular CPE mayhandle a plurality of connections, some bursty and others relativelyconstant, its bandwidth needs will generally vary.

Many of the data services facilitated by the system 100 of FIG. 1 arebursty and delay-tolerant. Because bandwidth is provided to theseservices on a demand assignment basis as needed, these services arecommonly referred to as Demand-Assigned Multiple Access or “DAMA”services. When a CPE 110 needs to request bandwidth for a DAMA serviceit transmits a bandwidth request message to the base station 106. Thebandwidth request messages communicate the immediate bandwidthrequirements for the DAMA service. The bandwidth requirements can andtypically do vary over time. The quality of service or “QoS” for theDAMA connection may be established when the CPE connection is initiallyestablished with the base station. Therefore, the base station has theability to access or “look-up” the QoS for any DAMA service that it iscurrently accommodating.

As described above, the CPEs 110 have a number of different techniquesavailable to them for communicating bandwidth request messages to theirassociated base stations. One such technique is by transmitting abandwidth request message in response to being polled by a base station.In accordance with the basic polling technique, the base stationallocates bandwidth to selected CPEs specifically for the purpose ofmaking bandwidth requests. The bandwidth for requests may be allocatedto individual CPEs, or to multicast groups of CPEs. As described in moredetail below in the subsection which describes the group or multicastpolling technique, allocations to multicast groups of CPEs definebandwidth request contention slots, and simultaneous responses willlikely collide, requiring resolution of the collisions. Advantageously,the bandwidth allocations are not made in the form of explicit messages,but rather they are made in the form of bandwidth allocation increasesin the transmitted map describing the uplink sub-frame 400 (FIG. 4). Inan exemplary system, polling is performed on a per-CPE basis, whilebandwidth is requested by the CPE on a per-connection-ID basis, andbandwidth is allocated on a per-CPE basis. These concepts are describedin more detail below.

Reservation-Based Polling Technique (Individual Polling)

When a CPE (or other user entity) is polled individually, no explicitmessage need be transmitted to poll the selected CPE. Rather, the CPE isallocated bandwidth in the uplink sub-frame map that is sufficient toallow the CPE to respond with a bandwidth request. Specifically, thebase station allocates bandwidth in the CPE scheduled data block 406(FIG. 4) for the selected CPE that is sufficient to allow the selectedCPE to respond with a bandwidth request message. If the selected CPEdoes not require more bandwidth, it returns a request for zero bytes. Azero byte request (rather than no request) may be used in the individualpolling process because explicit bandwidth for a reply has already beenallocated. Users other than CPEs, such as individual connections andconnection groups, may be similarly polled by providing bandwidth to theuser without an explicit message. Alternatively, in someimplementations, if a CPE does not require more bandwidth, unusedbandwidth resulting from the polling of the CPE may be padded with fillbytes, implying a request for zero bytes.

In some systems, even the basic communication unit allocated to a CPE oruser for the purpose of requesting bandwidth can be multiplexed toinclude both user data and a bandwidth request. In most systems, such abasic communication unit may be defined to include at least user dataand a “poll-me” request. A CPE can efficiently utilize the bandwidthallocated to it by including both user data and, if needed, apiggybacked bandwidth request or polling solicitation in the sameallocated bandwidth.

Inactive users, and active users which explicitly request to be polledby setting a “poll-me” message within existing bandwidth, are eligiblefor individual polling. Active users that do not set a respective“poll-me” message will not generally be polled individually, since theiraccess to existing bandwidth makes them capable of alternatives, such aseither piggybacking a bandwidth request or at least setting a poll-memessage. Individual polling is very useful for users which havemomentarily suspended transmissions. The rate of polling may adaptivelydepend, for example, on the duration of the user's suspension. Users ofactive CPEs respond to polling using the modulation scheme currently inuse. However, responses by or via inactive CPEs may use a QAM-4 orsimilarly robust modulation scheme to ensure that the transmission canbe detected by the base station even under adverse environmentalconditions.

It is desirable to ensure timely responses to requests for morebandwidth for a constant bit rate service such as a channelized T1service in which channels may be added or dropped dynamically. To ensurethat the base station responds quickly to requests for more bandwidthfor a constant bit rate service, the uplink bandwidth allocated to aconstant bit rate service that is not currently operating at a maximumrate may be made sufficiently large to accommodate both the service'scurrent rate and a bandwidth request.

The information exchange sequence for individual polling is shown in theflow diagram of FIG. 5. As shown in FIG. 5, the base station may haveseveral layers of control mechanisms or protocol stacks 502, 504 and 506that control, among other things, the bandwidth request and allocationprocess. The base station MAC is sub-divided into two sub-domains: (1)the high level media access arbitration (HL-MAA) MAC domain 504 and thelow level media access arbitration (LL-MAA) MAC domain 506. In anexemplary embodiment, the LL-MAA MAC domain spans exactly a physicalchannel, and each physical channel requires an instance of the LL-MAAMAC domain. The HL-MAA MAC domain spans multiple physical channels,typically all physical channels in the same sector. A MAC domaincomprises an HL-MAA MAC domain and the LL-MAA MAC domains associatedwith the physical channels within the HL-MAA MAC domain.

As shown in FIG. 5, the base station individually polls a CPE (asindicated by control arrow 508) by allocating bandwidth sufficient forthe CPE to respond with a bandwidth request message. This bandwidth istypically allocated in an uplink sub-frame such as sub-frame 400. If theCPE MAC 510 determines that there is data to be sent for a selectedconnection k (typically under direction of a higher CPE control layer512 via a control path 514), then the CPE MAC control mechanism issues abandwidth request 516 to the base station MAC 506. If there isinsufficient bandwidth available to the CPE 110 as determined by thebase station's LL-MAA 506, the bandwidth request will not be granted.Else, the bandwidth request will be granted, and the grant implicitlycommunicated to the CPE MAC 510 by the base station allocatingadditional bandwidth to the CPE in the uplink sub-frame 400, asindicated by the control path 518. The CPE will then begin transmittingdata to the base station over the uplink using the bandwidth it has beenallocated.

FIG. 6 is a flow diagram showing an exemplary individual pollingtechnique 600 for CPEs, though the techniques are generally alsoapplicable to users other than CPEs. As shown in FIG. 6, the methodstarts at decision STEP 602 to determine whether bandwidth is availablefor the purpose of individually polling the CPEs. If no more bandwidthis available for individually polling the CPEs 110 then the methodproceeds to STEP 604 to initiate multicast or broadcast polling asappropriate, techniques which are detailed in a later sub-section.However, if sufficient bandwidth is available for the purpose ofindividually polling CPEs, the method proceeds to a decision STEP 606whereat a determination is made whether there are any unpolled activeCPEs that have a “poll-me” bit set. If so, the method proceeds to acontrol point 608. If not, the method proceeds to a decision STEP 610whereat it determines whether there are any unpolled inactive CPEspresent. In other embodiments, decision STEP 610 may check for otherconditions, such as unpolled CPEs whose polling period has elapsed sincethe previous poll. If decision STEP 610 is satisfied, the methodproceeds to the control point 608. If not, the method proceeds to acontrol point 612.

The method proceeds from the control point 608 to STEP 614 toindividually poll the selected CPE. As shown in FIG. 6, at STEP 614 thebase station initiates the polling of the selected CPE and marks the CPEas polled. Thus, by this method all inactive CPEs, along with unpolledactive CPEs requesting polling by setting their respective “poll-me”bits, are individually polled. In alternative embodiments STEP 614includes sub-steps to refine the polling policy for each user or groupof users. Such sub-steps may evaluate one or more communicationparameters for the inactive user such as a quality of service requiredfor that user either to ensure data integrity or according to contractguarantees, and recent or average rate of bandwidth usage. A rate ofpolling may be selected which is a substantially continuous functionbased on the one or more user's parameters. The rate can be asubstantially continuous function of the parameters, if a large number(e.g., over 50) of different rates may be derived from the applicableparameters, and if selected rates are derived from the parameterswithout restricting them to a limited number of preselected ratecategories. The selected rate may be represented as a desired timebetween polls. A further sub-step of STEP 614 may then check whether thedesired time between polls has elapsed for a particular user, and thepolling and marking of STEP 614 may be restricted to those inactiveusers which have met or exceeded their desired time between polls.

Actions which effect polling are shown diagrammatically in FIG. 6 in thecaption box 614′. The caption box 614′ of FIG. 6 shows the downlinksub-frame map 300 described above in FIG. 3. The MAC control portion 314of the MAC frame control header 302 may include an uplink sub-frame map400′. The uplink sub-frame map 400′ is communicated to the CPE MAC whenthe base station transmits this information to the CPE via the downlink.As shown in FIG. 6, and responsive to the polling STEP 614, the basestation MAC allocates additional bandwidth to the selected CPE (in FIG.6 this CPE is referred to as CPE “k”) in the uplink. This increasedbandwidth allocation is communicated to the CPE k via the uplinksub-frame map 400′.

As shown in FIG. 6, the method then returns to the decision STEP 602 todetermine whether there is more bandwidth available for individuallypolling the CPEs. When it is determined (at the decision STEPS 606 and610, respectively) that there are no active CPEs having a poll-me bitset and that there are no unpolled inactive CPEs present, the methodproceeds to a decision STEP 616. At the decision STEP 616, the methoddetermines whether any individual polls were performed. If not, themethod proceeds to a control point 618 and the method subsequentlyterminates at the termination step 620. However, if individual pollswere performed, the method proceeds to a STEP 622 to await theindividual bandwidth requests from the CPE that was polled (e.g., CPE“k”). As shown in the caption 622′ of FIG. 6, this bandwidth request 430is generated by the polled CPE (e.g., CPE “k”) during the CPE scheduleddata block 406 scheduled for the selected CPE in the uplink sub-frame400. In one embodiment, all data includes a header that indicates thetype of data being transmitted. For example, in this embodiment, controlmessages have associated CPE-unique connection identifiers that areassigned to them when the CPE registers. The structure of the controlmessages allows a base station to determine that a control message is abandwidth request.

As shown in FIG. 6, the method proceeds from STEP 622 to a decision STEP624 to determine whether any bandwidth requests were received. If not,the method terminates. However, if so, the method proceeds to a STEP 626whereat a bandwidth allocation method is initiated. As described in moredetail below, the base station uses a bandwidth allocation method toallocate bandwidth to the requesting CPE. The bandwidth allocation isindicated to the CPE by making appropriate changes to the uplinksub-frame map 400′. The method then terminates at STEP 620.

Contention-Based Polling Technique (Multicast and Broadcast Polling)

As described above with reference to STEP 604 of the individual pollingmethod of FIG. 6, if there is not sufficient bandwidth available for thepurpose of individually polling the CPEs, the base station MAC may pollthe CPEs in multicast groups, and may issue a broadcast poll to allCPEs. Multicast polling may be efficient despite the risk of collisioncreated by the technique. For example, when a particular user does notuse bandwidth for a period of time, the probability that bandwidth willbe requested at any particular time shrinks. As the probability ofneeding bandwidth shrinks, individual polls become more likely to draw anegative response (thus using bandwidth for no productive purpose),while including the user in multi-cast polls becomes less likely tocause bandwidth-wasting collisions. Consequently, it becomesprogressively more efficient to poll a plurality of such inactive usersat the same time, using a single contention slot of bandwidth to providerequest opportunities to the plurality of users.

In order to minimize the probability of collisions when multicastpolling must be used to conserve bandwidth, users may be polled ingroups as small as two users. A significant portion of bandwidth neededto individually poll any given number of users may be saved by multicastpolling the users, even in small multicast groups. In this event, it isdesirable that the probability of collision, multiplied by the averagebandwidth consumed to resolve such collision, is less than the timerequired for the individual polls which are avoided by the multicastpolling. Probability of a collision may be estimated based on the timesince last bandwidth use, the expected rate of bandwidth use, and timesince the last poll.

In order to reduce collisions by effectively reducing the polling groupsize, multicast polling group members who are individually polled in anuplink subframe may be precluded from responding to a multicast poll inthe same subframe. When this process results in only two eligiblerespondents in a multicast polling group, then responses identified asprobably collisions can be interpreted as bandwidth requests by each.Users which have been individually or multicast polled may be precludedfrom responding to a broadcast poll, which may thus provide theremaining users an opportunity to request bandwidth.

Multicast polling may be handled differently when the user entity is,for example, a connection rather than a CPE. Discrete CPEs generallyhave. no information regarding bandwidth needed by other CPEs in thesame multicast poll contention slot. However, because a CPE handlingcommunication to a plurality of individual connection “users” mustcoordinate bandwidth request transmissions from different users,“collisions” between competing users at a particular CPE can be resolvedby consolidating higher priority bandwidth requests, and postponinglower priority requests while setting the “poll-me” message in theallocated packet. Because of the bandwidth request coordination whichcan be performed by a CPE, multi-cast polling a plurality of discreteusers serviced by a particular CPE can be relatively efficient.

Multicast polling is preferably accomplished by special “addressing” oridentification of bandwidth allocations indicated in the uplink subframemap. This is best understood in the context of an exemplary overalladdressing scheme. The addressing of CPEs may be performed as follows:each CPE is assigned a unique permanent address (e.g., in one embodimentthe CPE has a 48-bit address) that is used in the registration process;and each CPE is also given a basic connection ID (e.g., in oneembodiment the CPE is given a 16-bit basic connection ID and a 16-bitcontrol connection ID during the registration process). Each servicethat is provisioned for a selected CPE is also assigned a connection ID.Connection IDs are generated by the base station MAC (specifically, bythe base station HL-MAA) and are unique across an HL-MAA MAC domain. Thebasic connection ID that is assigned when the CPE is registered with abase station is used by the base station MAC and the CPE MAC to exchangeMAC control messages between the CPE and the base station. The controlconnection ID (also assigned during registration) is used by the basestation and the CPE to exchange control and configuration informationbetween the base station and the CPE higher levels of control.Sub-groups of connections communicating via the CPE may also beidentified at both the CPE and base station ends with a groupdesignation, and may be treated as discrete users. Bandwidth requestsare processed from discrete users, and bandwidth is generally allocatedto discrete users; such users must be identifiable, and may be a CPE, anindividual connection, or a sub-group of connections.

Certain connection IDs may be reserved for multicast groups, sub-groupusers, and broadcast messages. Of all of the addresses available, aportion may be reserved for multicast use. For example, if the fourmost-significant bits of the connection ID are set to logical ones (hex“Fxxxx”), the address is interpreted as being set aside for multicastuse. This provides a total of 4K distinct multicast addresses. Oneexample of such a multicast use is for the distribution of a videoservice. The connection ID used to indicate a broadcast to all stationsmay be (0xFFFF) (i.e., all 16 bits are set to a logical one). Each usermay recognize a specific user identification, and also a number ofdifferent multicast polling addresses for multicast groups of which theuser is a member. One of the recognized multicast polling addresses willgenerally be a broadcast polling address.

As with the individual polling technique described above with referenceto FIGS. 5 and 6, the multicast polling message need not be explicitlytransmitted by the base station to the CPE. Rather, the multicast pollmessage is implicitly transmitted to the CPE when the base stationallocates bandwidth in the uplink sub-frame map. However, rather thanassociating allocated bandwidth to a user's specific basic connection IDas done when performing an individual poll, the base station associatesthe allocated bandwidth to a multicast or broadcast connection ID. Eachuser will preferably respond to the base station using bandwidthspecifically addressed to it if available, using bandwidth provided fora multicast polling address if no bandwidth is specifically addressed toit, and responding to a broadcast poll only if no bandwidth is availablefor either its specific address or a multicast group.Multicast/broadcast bandwidth allocation is shown in themulticast/broadcast uplink sub-frame map 400″ shown in FIG. 7. It isinstructive to compare the uplink sub-frame 400 (FIG. 4) used by thebase station when individually polling the CPEs, with the uplinksub-frame map 400″ of FIG. 7. FIG. 7 shows the uplink sub-frame mapwhich is transmitted in the MAC control portion of the downlink.

As shown in FIG. 7, the multicast/broadcast uplink sub-frame map 400″includes registration contention slots 402″ that map the registrationcontention slots 402 of FIG. 4. Rather than associating allocatedbandwidth with a selected user's specific basic connection ID, theallocated bandwidth is associated with a reserved registration ID, e.g.,033 0000. As further shown in FIG. 7, the uplink sub-frame map 400″ mayinclude a plurality of separate multicast group bandwidth requestcontention slots 404″, 404′″, etc. As shown, a number of PSs areprovided for each contention slot, and they provide adequate time for anumber of non-colliding bandwidth request packets by as many differentusers which belong to the multicast poll group indicated by the address,e.g. 0xF000. When a contention slot encompasses a plurality of bandwidthunits, the user may be instructed to utilize a random portion of anysuch contention slot. Alternatively, the user may be expressly directedto utilize a particular part of such slot, such as first, third, or lastbandwidth unit within the contention slot. Such bandwidth units willvary with the architecture of the system, but may for example be asingle PI (defined by the system coding scheme), or a minimum packetsize. The uplink sub-frame map 400″ may also include broadcast bandwidthrequest contention slots 410, reserved for an address recognized forthis purpose, e.g. 0xFFFF. Finally, similar to the uplink sub-frame ofFIG. 4, the uplink sub-frame map used to initiate multicast or broadcastpolls may include a plurality of CPE scheduled data blocks 406″, 406′″,etc., to transport uplink traffic data.

FIG. 8 is a flowchart showing a multicast and broadcast polling method800. As shown in FIG. 8, the group polling method 800 proceeds from aninitial step 802 to a decision STEP 804 whereat the method determineswhether there is sufficient bandwidth available for multicast polls. Ifsufficient bandwidth is available for multicast polls, the methodproceeds to a STEP 806 to poll the next multicast group in the MACcontrol portion 314 of the MAC frame control header 302. However, ifthere is insufficient bandwidth available to perform a multicast poll,the method proceeds to a decision STEP 808 whereat the method determineswhether there is sufficient available bandwidth for performing abroadcast poll. If so, the method proceeds to a STEP 810. If not, themethod proceeds to a decision STEP 812.

As shown in FIG. 8, at the STEP 810 a broadcast poll is initiated byplacing the broadcast poll in the MAC control portion 314 of the MACframe control header 302. Similar to the individual polling technique,the multicast poll message is implicitly transmitted to the CPE byallocating bandwidth in the uplink sub-frame map 400″. The allocatedbandwidth is associated with a multicast or broadcast connection ID.

At the decision STEP 812 the method determines whether a broadcast ormulticast poll was initiated. If so, the method proceeds to a STEP 814whereat the method monitors the appropriate bandwidth request contentionslots (e.g., as defined by the bandwidth contention slot descriptions404′, 404′″, and the broadcast bandwidth request contention slotdescriptions 410 of FIG. 7). If no broadcast or multicast poll wasinitiated, the method proceeds to control point 816 and then terminatesat a termination STEP 818.

The method proceeds from the monitoring STEP 814 to a decision STEP 820to determine whether valid (i.e., non-colliding) bandwidth requests weredetected. If no valid bandwidth requests were detected at STEP 820, themethod proceeds to the control point 816 and terminates at terminationSTEP 818. However, if the method detects valid bandwidth requests, themethod proceeds from STEP 820 to STEP 822. At STEP 822 the method uses aconvenient bandwidth allocation algorithm to allocate bandwidth to theCPE that requested bandwidth. A bandwidth allocation algorithm isdescribed below in more detail with reference to FIGS. 12-13. Thebandwidth is allocated in the uplink sub-frame map 400″ as shown in FIG.8.

When a poll is directed to a multicast or broadcast connection ID, usersbelonging to the polled group may request bandwidth by employing thebandwidth request contention slots (either the multicast contentionslots for the group specified or the broadcast bandwidth requestcontention slots 410) allocated in the uplink sub-frame map 400″. Inorder to reduce the likelihood of collisions, only CPEs needingbandwidth are allowed to reply to multicast or broadcast polls, suchthat zero-length bandwidth requests are not permitted in the bandwidthrequest contention slots. CPEs may transmit the bandwidth requests inthe bandwidth request contention slots (e.g., contention slots 404)using a modulation they are presently assigned, or may be required toemploy a more robust modulation such as QPSK. In an exemplaryembodiment, the contention slots are sized to hold a 1-PS preamble andbandwidth request message. Due to physical resolution characteristics ofthe coding scheme used, the message requires 1 PI (e.g. one Reed-Solomoncode), which may require six PS of 1.25 μs each using QAM-4 modulation,and correspondingly less PSs in higher modulations. In otherembodiments, two PIs is the smallest practical size for a message,formatted as an ATM cell. Multiple bandwidth request messages from thesame CPE may be multiplexed in a single bandwidth request contentionslot without increasing the bandwidth utilization or the likelihood ofcollisions occurring. This allows the same CPE to make multiplebandwidth requests in the same slot, whether the “user” is the CPE or isa subset of connections served by the CPE.

When multiple CPEs attempt to simultaneously utilize a given contentionslot which can only accommodate a single bandwidth request, a collisionwill occur. In order to reduce the likelihood of such collisions, amulticast poll may allocate sufficient bandwidth for a bandwidth requestcontention slot to accommodate a plurality of bandwidth requests. Eachof the CPEs which are members of the multicast polling group addressedmay be instructed to transmit their bandwidth requests randomly withinone of such request slots. Alternatively, the multicast polling groupcan be broken into as many different multicast polling sub-groups asthere are bandwidth request slots available, and the single multicastpolling contention slot may be broken into a plurality of distinctcontention slots each having, for example, only enough bandwidth for asingle bandwidth request. In this manner, only a few CPEs contend foreach bandwidth request slot.

Multicast polling is useful when there is insufficient time toindividually poll, within a suitable interval, all inactive users. It isparticularly efficient for servicing very low-usage users. The basestation is able to define contention periods both for multicast groupsand also for all users generally (i.e., broadcast). After user scheduleddata, CPE control messages, and polling bandwidth has been allocated,the base station may allocate all remaining unused time in the upstreamframe to contention for any combination of multicast bandwidth requestsand CPE registration requests.

A CPE needing to transmit in a contention slot which spans more than onebandwidth request period may randomly select a bandwidth request periodwithin the interval, and initiate a request transmission in the startingPS of the selected bandwidth request period. This randomizationminimizes the probability of collisions. Some systems ordinarilyutilizing plural-PI packets for normal data may recognize single-PIpackets as bandwidth requests or “poll-me” messages, thereby reducingthe likelihood of collisions during contention slots.

If an error occurs when performing either a multicast or broadcast poll(such as the detection of an invalid connection ID) the base stationtransmits an explicit error message to the CPE. If the base station doesnot respond with either an error message or a bandwidth allocationrequest within a predefined time period, the CPE will assume that acollision occurred. In this event, a contention resolution process mustbe initiated.

Contention Resolution Process

A collision is presumed if there is no response from the base station tothe request within a pre-defined time period, whereupon a pre-definedcontention resolution process is desirably initiated. For example, theCPE may use the well-known “slotted ALOHA” contention resolution processto back off and try at another contention opportunity.

The following resolution process may be used: Assuming that the initialbackoff parameter is i and that the final backoff parameter is f,

1. On the first collision, the CPE waits a random interval between zeroand 2^(i) contention opportunities and then tries again.

2. If another collision occurs, then the interval is doubled and the CPEtries again, repeating until the interval 2^(f) is reached.

If the CPE is still unsuccessful, an error is reported to the systemcontroller and the contention process is aborted. Other contentionresolution mechanisms can be used, such as the well-known Ternary treemechanism.

Poll-Me Message

As described above with reference to FIGS. 3-8, a currently active CPEmay set a “poll-me” or a “priority poll-me” bit or message in a MACpacket in order to indicate to the base station a need for furtherbandwidth allocation. For example, a selected CPE may request a poll bysetting a poll-me (“PM”) bit in the MAC packet header. Similarly, aselected CPE may set a priority poll-me (“PPM”) bit in the MAC header inorder to indicate that a priority poll is desired. Those skilled in theart will understand that though the PM bit and the PPM bit are describedas a bit, they may be implemented as any convenient messagecommunicating a need to be polled. For example, they may be indicated byone or more of 16 possible control messages in a 4-bit control message,or one or two of 4 possible messages in a 2-bit control field. While alarge dedicated poll-me message field will consume significant effectivebandwidth, multiple-bit messages can be efficient. For example, atwo-bit poll-me message field can request 0, 1 or 2 bandwidth units,with one combination (e.g. 00) reserved to indicate that a furtherbandwidth message is disposed at some predetermined location elsewherewithin the packet. Such other location may be, for example, connectionID bits which are presently unnecessary, or may be disposed within atrailer in the payload of the packet. Such a request for furtherbandwidth within existing bandwidth units may be more like a “poll-me”message if it is disposed in a header field, or more like “piggybacking”if the request is disposed in the packet payload.

It is advantageous to avoid polling those users which already havebandwidth allocated except in response to a “poll-me” message. A“poll-me” procedure by which a CPE can stimulate a base station to pollthe CPE is shown in FIG. 9. When the base station detects a request forpolling, the polling process illustrated in FIG. 10 may be employed tosatisfy the request, if bandwidth is available.

FIG. 9 is a flow chart illustrating use of a poll-me bit by a CPE tostimulate polling. As shown in FIG. 9, the method first determines at adecision STEP 902 whether the “piggybacking” technique described in moredetail below has been exhausted. If not, the method proceeds to STEP 904and attempts to perform “piggybacking” first. The method then proceedsto a STEP 906 whereat the connection is set equal to a first connection.The method shown in FIG. 9 then proceeds to a decision STEP 908 todetermine whether any bandwidth needs exist. The bandwidth needs areexamined in this manner for each connection within the CPE in turn, forexample by observing that a packet identified with a particularconnection ID is completed for sending, or through a separate processfor tracking bandwidth needs and priorities. If the connection does nothave bandwidth needs, then the method proceeds to a STEP 916 and scansfor the next connection. If a bandwidth need exists, the method proceedsto a decision STEP 910. At STEP 910 the method determines whether anymore packets are available for accommodating the poll-me bit. If not,the method terminates at the STEP 910. However, if packets areavailable, the method proceeds to a STEP 912 and sets a poll-me bit inan available packet. The STEP 912 may also include preparation of thepacket which will be transmitted when bandwidth is allocated to the CPEby the base station polling the CPE; for example, after a firstconnection is found to need bandwidth, the poll-me bit may be set and afirst bandwidth request disposed in the packet which will be sent inresponse to polling bandwidth, and after a second connection isdetermined to have bandwidth needs, the responsive packet may bemodified to contain a second bandwidth request. Thus, the number ofpackets to be requested when the requested polling bandwidth is receivedmay be determined as a part of this method. The packets requested may beidentified as to simply number, with or without parameters such aspriority and/or connection or connection group identification.

FIG. 10 shows a message sequence that may be used in requesting pollsusing the “poll-me” message described above. As shown in FIG. 10 at dataconnection 930, the CPE initiates a polling sequence by setting apoll-me message in the MAC header of a connection packet. The basestation MAC responds via data message 932, individually polling theselected CPE by allocating bandwidth to the selected CPE in the uplinksub-frame map. The selected CPE subsequently responds with a bandwidthrequest disposed in communication 934, which is sent to the Base Stationin the uplink bandwidth which was allocated in downlink message 932. Inresponse to the CPE's bandwidth request, the base station grantsbandwidth and allocates bandwidth to the CPE in the uplink sub-frame mapas shown in communication path 936. The selected CPE then transmits datato the base station, typically for a connection which caused therequest, during the timeslots allocated for it in the uplink sub-framemap.

“Piggybacking” Technique

As described above, in order to reduce overhead bandwidth necessary forthe bandwidth allocation process, currently active CPEs may “piggyback”a bandwidth request (or other control message) on their currenttransmissions. The CPEs may piggyback bandwidth by using unusedbandwidth in packets of existing bandwidth allocations. A procedure forusing excess bandwidth in this manner is shown in FIG. 11.

The method shown in FIG. 11 initiates the piggybacking process at STEP950. The method proceeds to a decision STEP 952 to determine whether theCPE requires additional bandwidth. If so, the method proceeds to adecision STEP 954, if not, the method proceeds to a termination STEP 964whereat the method terminates. At the decision STEP 954 the methoddetermines whether any unused bytes exist in the current allocation. Ifso, the method proceeds to insert bandwidth requests into the unusedbytes at STEP 956. If not, the method proceeds to a decision STEP 958.At the decision STEP 958, the method determines whether any packets atall are allocated to the CPE. If there are no packets found at thedecision STEP 958, the method proceeds to STEP 960. However, if packetsare allocated, the method proceeds to a STEP 962 whereat the CPE sets apoll-me message (which may be a single bit, as discussed above) in apacket which is available but does not have enough unused bytes toaccommodate a complete bandwidth request. The method then proceeds tothe STEP 960 whereat the CPE awaits polling by the associated basestation. The method then terminates at the STEP 964.

Bandwidth Allocation

Much of the foregoing has focused on techniques and processes whereby abase station may determine bandwidth needs for all users. This processof obtaining bandwidth requests is part of the overall process ofcontrolling bandwidth allocation, which is one of the basic functions ofthe MAC (media access controller). As described above, the base stationMAC is responsible for allocating the available bandwidth of a physicalchannel on the uplink and the downlink. Within the uplink and downlinksub-frames of a particular communication physical channel, the basestation lower layer media access arbitration (LL-MAA) MAC schedulerallocates the available bandwidth between the various services sharingthe physical channel in response to user requests, taking into accountthe priorities and rules imposed by their contractual and physicalquality of service (QoS) requirements. A base station generally handlestraffic on a plurality of different physical channels. The traffic ondifferent physical channels, and sometimes load sharing between them, isgenerally provided by higher control sub-layers of the base station MAC.Thus, bandwidth is allocated between physical channels according toconnection assignments made by the high level media access arbitrationof the MAC (HL-MAA MAC) layer, while bandwidth is allocated within aparticular physical channel according to uplink and downlink sub-framemaps. The uplink and downlink sub-frame maps may be sharing time on thesame carrier frequency (TDD) or may each have their own distinctfrequency (FDD). In either direction of transmission (uplink ordownlink), bandwidth allocation is possible by any “multiple access”technique; that is, the shared medium may be divided according to timeincrements (TDMA), code division units (CDMA), or a combination of thetwo. The embodiments described herein primarily describe TDMA techniquesfor sharing the media, but the skilled person will be able to practicethe techniques described herein using CDMA techniques as well. CDMAaccess units, i.e. a particular code within a broad channel, may beutilized in place of the physical slot (PS) units which are describedmost frequently herein. In many cases, basic CDMA bandwidth units arelarger than the PIs described herein, so that bandwidth would be dividedsomewhat more coarsely. However, the CDMA access units may be furthersubdivided using TDMA techniques to provide finer bandwidth divisions.In either event, the resulting bandwidth divisions may be utilized ingenerally the same manner as PS or PI units described herein.

Downlink Bandwidth Allocation

Referring first to FIG. 2, the base station will have some number of thePSs in a TDM frame available for downlink transmissions; for ATDDoperation, the number depends upon the ATDD split 210 shown in FIG. 2.First, the base station allocates PSs in the downlink frame for PHYControl and enough PSs for at least 1 PI for the MAC Control. The basestation may calculate uplink bandwidth allocation before downlinkbandwidth allocation in order to determine the number of PIs to allocatefor the MAC Control. In one embodiment, the PHY Control and MAC Controlare always sent using QAM-4 modulation, and is typically sent at amodulation level robust enough for all receiving CPEs.

The base station determines the number of PIs required to transmitpending downlink data for each CPE. This number is then converted to PSsas a function of the modulation used for the CPE associated with eachconnection. The data pending data is queued, as explained below,according to QoS or priority, and bandwidth is first allocated forhighest QoS data. For each remaining QoS, or until available bandwidthis entirely allocated, the base station determines if there is enoughbandwidth to satisfy the entire need of the QoS queue. If so, the basestation allocates the required bandwidth. Otherwise, if there is notenough bandwidth to satisfy the queue, the base station implements aqueue-specific fairness algorithm described elsewhere.

The downlink bandwidth may be allocated from queues as shown in FIG. 12.By this procedure, the base station MAC maintains a set of queues foreach physical channel (e.g. 1202-1208) that it serves. Information fortransmission to particular connections arrives from higher layers 1210,and is mapped in a destination mapping step 1214 under the control ofthe HL-MAA MAC sublayer 1220. Within each physical channel queue set1202-1208, the base station may maintain a queue for each QoS orpriority. The queues hold data that is ready to be transmitted to theCPEs present on the physical channel. The higher layers 1210 of the basestation protocol stack (which may be realized in software, or inhardware such as an ASIC) are responsible for the order in which data isplaced in the individual queues within the physical channel queue sets1202-1208. The base station higher control layers, e.g. the HL-MAA MACsublayer 1220, are free to implement any convenient fairness or trafficshaping algorithms regarding the sharing of access between connectionsat the same QoS, without impacting the base station lower layer mediaaccess arbitration (LL-MAA) MAC control layers 1232-1238. Once data ispresent in the queues it is the responsibility of the base stationLL-MAA MAC sublayers 1232-1238 (e.g., the BS LL-MAA of FIGS. 5 and 10)to allocate bandwidth based on the QoS.

In determining the amount of bandwidth to allocate at a particular QoSfor a particular CPE, the base station may take into account the QoS,modulation, and the fairness criteria used to keep an individual CPEfrom demanding excessive bandwidth. Such arbitration activity isrepresented by the sketched program steps shown in LL-MAA MAC sublayer1232; it will be understood that many hardware and softwareimplementations of such arbitration are possible. For example, bandwidthmay be allocated in QoS order. If there is a queue that cannot betransmitted entirely within a particular frame, a QoS specific fairnessalgorithm, such as fair-weighted queuing, may be used within that queue.According to this process, each connection is given a portion of theremaining available bandwidth based upon the relative weight of theconnection. The derivation of connection weights is QoS-dependant. Forexample, ATM traffic may be weighted based upon contractual bandwidthlimits or guarantees for each connection. IP and other delay-toleranttraffic, such as Ethernet, or ATM traffic encapsulating suchdelay-tolerant traffic, may all receive identical weights, or may beadjusted for contractual QoS guarantees. The allocated data is sortedfor modulation type, which affects the portion of available timeconsumed for each allocated connection unit.

A downlink frame (or subframe, in the case of any form of TDD) providedfor a particular physical channel by, e.g., the LL-MAA MAC sublayer 1232may include a preamble 1242, physical connection control information1244, MAC control information 1246, data 1250 for a CPE 1 connectionhaving a QoS of 1 (high priority), data 1252 for another connection ofCPE 1 which has a lower QoS, data 1256 for a CPE k at QoS 1, and data1258 for another connection of CPE k which has a lower QoS. The firstportions 1242, 1244 and 1246 of the data are generally provided to allCPEs sharing the channel. As such, this first portion will generally besent first and at the most robust modulation required by any CPE. Suchrobust modulation may be, for example, QAM-4, QAM, or quadraturephase-shift keying (QPSK). If any part of the downlink is broadcast, andif some inactive CPEs do not have an established modulation, then themost robust modulation available may be used.

As can be seen, then, the data which was organized by target CPE ispreferably reorganized by the modulation technique presently used by theCPE. The preamble 1242 and other control data 1244, 1246 is shownorganized for transmission in the first transmission block 1260 at theControl modulation of QAM-4. The modulation used in the first modulationblock 1260 is generally the most robust modulation of the downlink frame(or subframe). While in this case it is indicated to be QAM-4, theskilled person will understand that even more robust modulations such asQAM may be necessary for the transmission block 1260, and that higherspeed but less robust modulation types such as QAM-16 may be acceptable,depending on the characteristics of the least robust connection served.Next, it is shown, representatively, that the data 1256 and 1258 for CPEk is at the next lower modulation level QAM-M1, in modulation block1264, which is separated from the first modulation block 1260 by themodulation transition gap 1262. M1 is a different modulation from thatused in the modulation block 1260, and preferably is the next mostrobust modulation level which is needed. In this way, each CPE whichwill accept data from within a later modulation block will be able tokeep track of the data in preceding blocks so as not to loseregistration to the preamble. Each CPE does not need to have a differentmodulation used, and the skilled person will appreciate that if CPE krequired instead the lowest modulation, as is used in modulation block1260, then the data for CPE k could be concatenated with the controldata within the modulation block 1260. Similarly, data for manydifferent CPEs having the same modulation level may be transmitted inthe same modulation block, e.g. 1264, 1268 or 1272. As shown in FIG. 12,CPE 1 utilizes a significantly faster (and less robust) modulationQAM-M3, and accordingly the data 1250 and 1252 for CPE 1 is reorganizedso as to be transmitted in transmission block 1272. Transmission block1272, at modulation QAM-M3, is separated from transmission block 1268,which utilizes modulation QAM-M3, by a modulation transition gap 1270,and is separated from later modulation blocks (or possibly from uplinksubframes in TDD systems) by modulation transition 1274. Data forunspecified CPEs is shown as being ordered by modulation intotransmission block 1268 (at QAM-M2) and transmission block 1272, but theskilled person will appreciate that data will be ordered into any andall of the transmission blocks which are used.

Uplink Bandwidth Allocation

The ATDD split described above with reference to FIG. 2 will generallyprovide at least some PSs in the TDD frame available for uplinktransmissions (in FDD, all uplink slots are available each frame, and inordinary TDD a fixed quantity of uplink slots are available for eachsame-sized frame). In order to determine how to allocate the availableuplink bandwidth, the base station may maintain an estimate of the dataand control messages pending at each QoS for the CPEs that it serves,based upon received bandwidth requests and observed actual data traffic(i.e., connection establishment, “poll-me” messages, etc.). Pendinguplink bandwidth at each priority or QoS may be calculated and grantedseparately, so that bandwidth may be allocated for the highest priorityQoS data first, while lower QoS data is balanced against other CPE needsat that QoS. Expected uplink bandwidth from each user (or from aplurality of users sharing the same CPE or modulation) is converted to anumber of PIs required to communicate the data. The number of PIs isthen converted to a required number of PSs, based on the modulation.

Bandwidth is generally allocated for the highest QoS data first. Forexample, Continuous Grant (CG) connections having a current bandwidththat is less than the maximum bandwidth may be allocated uplinkbandwidth that is the smaller of: 1) their maximum bandwidth, or 2)their current bandwidth plus the bandwidth necessary to send a CGbandwidth change message. Noncompressible CG always receives theirmaximum grant.

For each remaining QoS, or until available bandwidth is entirelyallocated, the base station determines if there is bandwidth sufficientto satisfy the entire need of the QoS queue and it then allocates therequired bandwidth. Otherwise, the base station implements aqueue-specific fairness algorithm, as described elsewhere.

An exemplary uplink bandwidth allocation method, shown in FIG. 13 isvery similar to the downlink bandwidth allocation method described abovewith reference to FIG. 12. However, rather than being maintained by thebase station, the data queues are distributed across and maintained byeach individual CPE, e.g. 1310, 1320 and 1330. Rather than check thequeue status directly, the base station may receive requests forbandwidth in the uplink communications, e.g. 1318, 1328 and 1338 fromthe CPEs using the techniques described above with reference to FIGS.3-11. Using these bandwidth requests, received for each channel by aLL-MAA MAC, e.g. 1352, the base station 1350 may reconstruct logicalpictures, e.g. 1354, 1356 and 1358 of the state of the CPE data queuese.g. 1314, 1324 and 1334 to form an overall uplink queue picture 1362 ofthe entire channel. Based on this logical view of the set of queues, thebase station allocates uplink bandwidth in the same way as it allocatesdownlink bandwidth. As described above, the bandwidth allocated to anyselected CPE is transmitted to the selected CPE in the form of bandwidthbeing allocated in the uplink sub-frame map for the selected CPE. Suchtransmission may be included in control information 1340 which istransmitted from the base station LL-MAA 1352 to each CPE sharing thechannel. The selected CPE may then allocate this bandwidth across itsconnections, if the CPE is the “user” level; otherwise, the bandwidthmay be identified for particular connection users or connection groupusers within the CPE. The user CPE may use the bandwidth in a differentmanner than expected, for example if it receives higher priority datawhile awaiting the bandwidth allocation. It is also possible to have aCPE serving lower level users, such as connection users, to coordinatebandwidth requests from a plurality of its users, and to negotiatereallocation of allocated bandwidth between different users ifconditions change. As described above, the bandwidth allocations are ina constant state of change owing to the dynamic nature of bandwidthrequirements. Consequently, a selected CPE may receive unsolicitedmodifications to the bandwidth granted on a frame-by-frame basis. If theselected CPE user is allocated less bandwidth for a frame than isnecessary to transmit all waiting data, the CPE may use the QoS andfairness algorithms to service its queues. The CPE user may “steal”bandwidth from lower QoS connections to piggyback requests for morebandwidth using the piggybacking technique described above.

FIG. 13 shows connection from the representative LL-MAA MAC sublayer1350 to the HLL-MAA MAC sublayer 1360, which may for example reassignphysical channels to share loads. It should be understood that a givenCPE may well be connected to a particular base station by two or morephysical channels, permitting such load sharing between physicalchannels. In this event, CPE 1310 may have duplicates (not shown) of thequeues 1314 and the LL-MAA MAC 1316. Similarly, while the MACs 1326 and1336 are LL-MAA MACs shown managing the connection of a single physicalchannel, duplicate LL-MAA MACs and queues may be needed for eachphysical channel handled by the CPEs 1320 and 1330.

QoS Specific Fairness Algorithms

Data for transmission on the uplink and the downlink is may be queued byquality of service (QoS) designations, and the data transmitted in orderof a QoS queue priority as described above. As the queued data istransmitted, there may be a QoS queue for which there is insufficientbandwidth to transmit all queued data during the current TDD frame. Whenthis situation occurs, a QoS specific fairness algorithm is initiated toensure fair handling of the data queued at that QoS. There are 3 basicfairness algorithms that can be implemented: (1) Continuous Grant; (2)Fair-weighted queuing; and (3) Round Robin.

The MAC need not police connections for bandwidth usage. Policing may beperformed by higher control layers. The MAC then assumes that allpending data has met contractual restrictions and can be transmitted.Continuous Grant queues have the simplest fairness algorithm. All datain these queues must be sent every TDD frame. Insufficient bandwidthindicates an error in provisioning.

Fair Weighted Queuing

Fair weighted queuing requires that all connections at a given QoS havea weight assigned to them to determine the percentage of the availablebandwidth they are eligible to receive. This weight value may bederived, for example, from one or more data rate parameters, dependingupon the contractual parameters of the provisioned connection. Threesuch parameters are: (1) Data Pending; (2) Guaranteed Rate; and (3)Average Rate.

Real-time VBR connections are established as DAMA connections withfair-weighted queuing based upon data pending. For a QoS queue of thistype in a TDD frame having insufficient bandwidth to transmit all of thedata in the queue, a weight for each connection in the queue isdetermined. In one embodiment, this weight is the amount of data pendingfor the connection expressed as a percentage of the total data pendingin the queue. Because the amount of data pending is dynamic, the weightsfor these types of queues must be determined every TDD frame where thereis insufficient bandwidth to send all data in the affected queue.

For DAMA connections contracted at a guaranteed rate the weights arecalculated based on the guaranteed rate. In this case, the weight may beexpressed as a percentage of the total guaranteed rate of allconnections with data pending in the queue. Because the guaranteed rateis provisioned the weights need not be determined each TDD frame wherethey are used. Rather, the weights for a queue are only determined whenthere is a provisioning change (i.e., a new connection, a change inconnection parameters, or a connection termination) for one of theconnections in the queue.

For DAMA connections contracted at an average rate, the weights may becalculated based on the average rate. The weight is the average rateexpressed as a percentage of the total average rate of all connectionswith data pending in the queue. Because the average rate is provisionedthe weights need not be determined each TDD frame where they are used.Rather, the weights for a queue are only recalculated when there is aprovisioning change for one of the connections in the queue.

In all of the cases described above, the granularity of the bandwidthallocations may be too coarse to provide a perfect percentage-basedweighted allocation across the connections in the queue. This may resultin some queues not receiving any bandwidth in a particular TDD frame. Toensure that the occurrence of this condition is fairly distributedacross the connections in the queue, the connection that did not receivebandwidth is given priority the next time the insufficient bandwidthcondition exists for the queue. For queues with weights based uponguaranteed or average rates some connections may not have sufficientdata pending to use all of the bandwidth that they are entitled to basedupon their calculated weight. In these cases, the connection's unusedbandwidth is fairly distributed across the connections having excessdata pending.

Some QoSs require that data be aged. For queues at these QoSs there isan associated queue of one step higher priority. If data is nottransmitted by the provisioned aging parameter, the data is moved to thehigher QoS queue and given priority over newer data in the originalqueue regardless of the relative weights of the connections.

Round Robin

The Round Robin fairness algorithm is used for best effort connectionswhere all connections have equal weight. When insufficient bandwidthexists to transmit all data in the queue in a particular TDD frameconnections are allocated bandwidth in a round-robin fashion with eachconnection receiving a block of bandwidth up to a queue-specificmaximum. Connections that did not receive bandwidth are given prioritythe next time the insufficient bandwidth condition exists.

Utilizing Allocated Bandwidth

Once a CPE is allocated bandwidth by the base station, the CPE, not thebase station, is typically responsible for using the uplink bandwidth ina manner that can accommodate the services provided by the CPE. The CPEis then free to use the uplink bandwidth that was allocated to it in amanner that is different than originally requested or granted by thebase station. For example, the service requirements presented to aselected CPE can change after the selected CPE requests bandwidth fromits associated base station. The CPE advantageously determines whichservices to give bandwidth to and which services must wait forsubsequent bandwidth requests. To this end, the CPE maintains a prioritylist of services. Those services having higher priority (e.g., thoseservices having high quality of service demands) will be allocatedbandwidth before those services having lower priority (e.g., IP-typedata services). If the CPE does not have sufficient bandwidth to meetits service requirements, the CPE will request additional bandwidthallocations by either setting its poll-me bit or by piggybacking abandwidth allocation request.

One advantage of having the CPE determine how to distribute itsallocated bandwidth is that it relieves the base station from performingthis task. In addition, the communication overhead that is required byhaving the base station instruct the CPE how to distribute its allocatedbandwidth is thereby eliminated, thus increasing usable systembandwidth. In addition, the CPE is in a much better position to respondto the varying uplink bandwidth allocation needs of high QoS dataservices. Therefore, the CPE can better accommodate the needs of thesetypes of service requirements than can the base station.

However, the CPE is not the only “user” which may be recognized by thebase station for bandwidth request and allocation purposes. Individualconnections, or groups of individual connections, may form discrete userentities. In that case, the CPE may not be given flexibility forallocating bandwidth, but rather may be required to provide bandwidthfor either data, or for bandwidth request, to specific user entitieswhich communicate via the CPE. Such requirement may readily becommunicated to the CPE via the connection identifier included with theprovided bandwidth; for example, a connection may be identified as adiscrete user or a member of a discrete user group as part of theconnection setup process during the initiation of the connection. Whensuch sub-CPE users are established, it may be advantageous to have theCPE consolidate bandwidth requests between different ones of its usersinto single packets.

Adaptively Providing Bandwidth Request Opportunities

In order to be able to quickly respond to communication needs, it isuseful to provide every user with frequent opportunities to requestbandwidth. As described previously, each of the various techniques forobtaining bandwidth requests are relatively more efficient under somecircumstances. For example, multicast polling may cause bandwidth to bewasted to resolve collisions. However, when CPE users are inactive forsubstantial periods, the frequency of their requests is low and theprobability of collision with other similarly inactive CPEs becomessmall. In this case “contention” polling, which uses very littlebandwidth in the absence of collisions, can efficiently provide frequentopportunities for users of inactive CPEs to request bandwidth.“Inactive” users may be divided into as many groups as bandwidth unitsare available, and one contention slot may then be assigned to each suchgroup. In order to accommodate such varying contention polling groups,it may be helpful to define many small polling groups including each newuser, so that a convenient polling group address is available whenneeded.

As the number of CPEs designated in each multicast poll decreases, thelikelihood that a particular CPE within the polling group will requestbandwidth may be allowed to increase. Thus, relatively more active CPEs(e.g. those which have had activity more recently, or which haveconnections expected to generate a bandwidth request soon) may beserviced by a multicast poll to a multicast poll group having only twoor three CPEs, without increasing the probability of a collision. Inthis way, the connection parameters of individual users, for example thebandwidth request probability of a CPE, can be used to adjust themembership of polling groups which are each serviced by multicastpolling at a particular rate, and also to adjust the polling rate ofsuch multicast polling. A higher rate of multicast polling decreases thelikelihood of collision and permits quicker response to a CPE's need forbandwidth. Conversely, of course, as the amount of available bandwidthfor multicast polling decreases, it may be necessary to provide acontention slot to a larger multicast polling group of “inactive” users.In this case, the definition of “inactive” may be made more stringent inorder to reduce the likelihood of a collision, so that only users with alow probability of making a bandwidth request are included in amulticast polling group having a large number of members.

It is often efficient to poll active CPEs at a zero polling rate, absenta request indicated by a “poll-me” message, because active CPEs haveopportunities to engage in “piggybacking” techniques or to send“poll-me” messages, as described above. Between the extremes of highusage which permits zero-rate polling, and low usage which can beefficiently serviced with multicast polling, moderate usage CPEs (orother users) may be given individual or reservation-based polling toprovide opportunities to request bandwidth without collisions.

For users (or groups of users) which are selected for individualpolling, the rate of polling for each user may be affected by acombination of one or more objective parameters specific to the user'scommunications, and may also be affected by objective parametersreflecting the shared medium generally, such as constraints on theshared physical channel. Examples of communication parameterscorresponding to a particular user (or group of users) include: a) timesince last bandwidth usage; b1) user QoS, or b2) for groups, number ofhigh-QoS connections or composite QoS; c) expected rate of bandwidthusage; d) measured rate of previous bandwidth usage; e) contractualguarantee of bandwidth availability and response time; and f) modulationlevel of physical channel, to name a few. Examples of parameters whichreflect the shared medium more generally include: i) availability ofbandwidth for the CPEs, i.e. available time in the uplink subframe; j)availability of high-QoS bandwidth, including low-QoS bandwidth whichcan be reallocated; k) a number of users for which individual polling isdesired; I) number of users at each modulation which do not presentlyhave allocated bandwidth, i.e. are paused or inactive; m) the averagetime, for groups of users, since using bandwidth; n) and othercomposites of parameters for groups of users in various categories.

The number of parameters general to the shared medium which can affectrates of individual polling is practically unlimited. It may be usefulto categorize some of these parameters into a finite number of possiblestates, and use only the categorized state values in determining pollingrates. Useful categorization may be better understood by examples. Thefollowing example is provided to illustrate a way to categorizecommunication parameters, and not to limit the scope of the claimedinvention.

As one example, users may be categorized according to relative recentactivity, with activity category I=“active,” category II=“no activityfor one to ten frames,” category III=“no activity for eleven to onehundred frames,” category IV=“no activity for one hundred and one to onethousand frames,” and category V “no activity for over one thousandframes.” In a simple example, all category II users may be individuallypolled at least once every three frames; if bandwidth is available,category III users are polled next, up to a maximum of once per fiveframes. Users in category IV may be grouped according to modulationlevel to form groups of three or fewer members, and each group may bemulticast polled at least once each five frames. All category V usersmay receive a single multicast poll at least every five frames.

FIG. 14 is a flow diagram showing method steps which may be employed bya base station to enhance the efficiency of obtaining requests forbandwidth allocations by adaptively applying more appropriate bandwidthallocation techniques as the conditions, particularly recent usage andQoS requirements, of CPEs changes. These method steps may be performedby a polling policy module of the system processing communications at abase station. Polling decisions are updated periodically; the decisiontree may be entered once per frame or once per two frames, or even lessfrequently. Note that while four polling groups (Active, RecentlyActive, Pausing and Inactive), as described below with respect to FIG.14, is convenient and effective for some systems, either more or lesspolling groups may be defined along the general lines of the foregoingdescription.

Entering the method described in FIG. 14 at STEP 1402, the base stationchecks the polling status of each CPE, and when none remain to bechecked, the procedure is done. Otherwise, at STEP 1404 a check is madefor outstanding bandwidth requests, which when satisfied will permit aCPE to piggyback a bandwidth request, or request polling. If the CPE hasan outstanding bandwidth request, then at STEP 1406 a timer TSR is setto −1; thereafter the next CPE will be checked. If there is no BWrequest outstanding, then at STEP 1408 two timers are incremented (orany other means for tracking time may be employed). The “time sincerequest” timer TSR generally tracks how long the CPE has been inactive,while the “time since poll” timer TSP tracks the duration of the pollingperiod.

At STEP 1410, a check is made whether it has been less than a short timeA since the CPE was active, and if so then the CPE is deemed to be inthe “active” polling group at STEP 1412, and the next CPE will then bechecked. The value of A may for example be one, two, or a number lessthan 10 frame periods, at least for 1 ms frame period systems. If TSR isgreater than A, then STEP 1414 determines if it is less than the largerquantity B. B may be a fraction of a second to several seconds, i.e. afew frames up to thousands of frame periods in the system describedabove. If TSR is less than B, the CPE is deemed “recently active” atSTEP 1416 and then will be individually polled. For such recently activeCPEs, the polling period may be fairly high. Thus, at STEP 1418 the timesince last poll TSP is compared to threshold Q. Q may range from about10 frames to hundreds of frames, depending in part upon the valueassigned to A. If TSP has exceeded the Q period, then at STEP 1420 theCPE is set up for an individual poll, which includes setting TSP=−1, andotherwise the next CPE is checked.

If TSR was not less than B, then at STEP 1422 TSR is checked for beingless than C. If TSR exceeds B but is less than C, then the CPE is deemedat STEP 1424 to be pausing, and that CPE will be polled at a perioddefined by S in STEP 1426. There, if TSP is less than S then a poll isnot needed yet and the next CPE is tested at 1402; but if TSP is notless than S, then the CPE is set up for an individual poll at STEP 1420.If TSR was not less than C at STEP 1422, then at STEP 1428 the CPE isdeemed Inactive, and is set up for periodic multicast polling asdescribed above, including setting TSP=−1. The multicast polling will beperformed at a rate defined elsewhere, for a plurality of different CPEswhich are all deemed inactive. As an example, a multicast poll may beprovided every 100 ms for each group of six or less Inactive CPEs.Groups for such multicast polls may usefully be selected according tothe modulation level of the CPE, because by performing the polling athigher modulation levels (e.g. QAM-64), less time is consumed for aphysical information unit for polling.

In the decision variables of FIG. 14, C is a greater value than B, andmay be many seconds or even many minutes. Typical values for A, B and Cmay be 2 ms, 2 s, and 2 minutes, respectively, but as explained thesevalues may vary widely according to the needs of the particularapplication. Typical values for Q and S may be 20 ms and 200 ms,respectively.

The values of each of the variables A, B, C, Q and S may be adaptivelyvaried depending upon the currently available bandwidth (or currentlyused bandwidth), or to the number of members of the defined groups. Forexample, the value of C may be decreased proportionally to a decrease inavailable bandwidth, in order to cause CPEs to be more quickly deemedinactive, so that multicast polling may be used and bandwidth savedthereby. Meanwhile, Q may be increased proportional to the number of“Recently Active” users, while S may be increased proportional to thenumber of “Pausing” users. Conversely, C may be increased, and Q and Sdecreased, proportional to an increase in bandwidth available forpolling. The skilled person will understand that a wide range ofadaptive algorithms may be constructed depending upon the particularcircumstances of an embodiment of the present invention.

At least two distinct types of quality of service (QoS) may beidentified and employed as communication parameters corresponding to theuser for adaptively modifying the techniques used for obtainingbandwidth requests. A first type of QoS is contractual, and representsthe performance which the communication system provider undertakes toguarantee to particular users. The second type is required by the natureof the communication connections serviced to ensure integrity of thecommunication. For example, constant bit rate (CBR) services such as thewell-known T1/E1, T2/E2, and T3/E3 lines each require bandwidthallocations which will enable the connection to convey data at regulartime intervals, within preestablished restrictions on the jitter anddelay of the time intervals, to ensure the integrity of thecommunication. These two different types of QoS may be included withinthe general term QoS, or may be distinctly specified, for example, as“contractual QoS” and “physical QoS.” These QoS parameters may be usedto determine the nature and rate of technique which is to be used todetermine bandwidth for a particular user.

The precise mixture of the foregoing techniques which will permit thebase station to most efficiently accept and respond to bandwidthrequests within the constraints of the service negotiated will, ofcourse, vary from system to system. The base station may adjust the“polling policy,” or method by which bandwidth requests will beobtained, for each CPE individually based upon an algorithm which isadapted for the system. In an exemplary embodiment, however, a limitednumber of polling policies may be defined, and each CPE may be assignedto utilize one of the defined polling policies. The group of CPEsassigned to utilize a particular polling policy thus forms a “pollingpolicy group.”

Per-User Adaptation of Bandwidth Request Techniques

As explained above, users may be adaptively assigned to different“polling policy” groups or categories, and the technique for obtainingbandwidth for a particular user may be determined by the group orcategory to which they are assigned. However, the technique forobtaining bandwidth requests may be adaptively determined for eachparticular user on the basis of the users parameters (and relevantchannel parameters) without reference to such “polling policy” groups.Such “per-user” adaptation is described below.

FIG. 15 is a flow diagram showing transitions in a polling state forindividual CPEs, which respond, for example, to the activity and QoS ofconnections to each CPE, in order to adaptively vary the procedure bywhich bandwidth requests are obtained from each CPE. The state tests maybe performed for each CPE periodically, such as every frame. The statetests may be initiated by leaving the “Done” state 1500 along path 1502.At 1510 a test may be performed for activity in the most recent frame.If there has been activity, then the CPE has had an opportunity torequest BW or at least request to be polled. Therefore, time sinceactivity (TSA) and time since poll (TSP) are both set to −1 at block1512. Thereafter, TSA and TSP are incremented at block 1514. Next, atest is made at block 1520 to see if activity is recent enough, i.e. ifTSA is less than a first threshold “A.” If less than “A” periods haveelapsed since activity, then the CPE may be categorized as “Active” atblock 1522. In many instances it will be unnecessary to poll activeconnections, since they have adequate opportunities to requestbandwidth, and accordingly Active CPEs may immediately proceed to Doneat 1500. If TSA is not less than “A,” then at 1524 a test may be made asto whether there are adequate constant bit rate (CBR) connections.Sufficient CBR connections exist when the CPE has a CBR connection of asufficient rate to allow the CPE to set a PollMe bit often enough tocause polling at a rate at least as fast as the selected FastPollingrate. In this embodiment, the presence of sufficient CBR connectionsmeans that there are sufficient uplink connections; moreover, the basestation provides uplink bandwidth to the user at the CBR rate.Accordingly, even though the CBR rate may be such that more time haselapsed since the last activity than “A,” it is preestablished thatuplink bandwidth will be provided soon enough and frequently enough toprovide opportunities for bandwidth requests which are sufficient tomeet the QoS requirements of the link. Thus, sufficient CBR activitywill have a similar effect as actual activity, such that the poll statefor such a CPE may also be set to Active, and the flow may proceed toblock 1500.

If the CPE is neither presently active, nor has enough CBR connections,then TSA may be tested again at block 1530 to see if TSA remains belowanother threshold, B (B should be greater than A). If so, then at block1532 the poll state of the CPE may be set to Fast Individual Polling. IfTSA is not less than B, the processing proceeds to block 1532 to testfor high QoS connections. The CPE poll state may also arrive at the FastPolling block 1532 via the decision 1534, if it has one or more high QoSconnections. Thus, the presence of one or more high QoS connections tothe user may prevent the user's polling state from reaching the slowpolling state 1542. If the CPE poll state is set to fast polling, thenat block 1560 the time since polling (TSP) of the CPE will be tested tosee if it is less than a threshold “F.” If it is, then the CPE has beenpolled recently enough and the processing is done for that CPE andframe. Processing proceeds to block 1500, which will generally be leftonly after the next frame is completed. If TSP is not less than F, thena flag may be set or other arrangement made so that the CPE will bepolled, as directed by block 1552. Once instructions for such poll arein place, the CPE is done for that frame.

If at block 1534 the CPE does not have high QoS connections, then it maybe tested to see if its TSA is still less than a threshold “C” (C shouldbe greater than B). If so, then the CPE's poll state may be updated atblock 1542. If not, the CPE will be tested at block 1544 to see if ithas medium QoS connections, which would provide another reason to haveits polling state set to Slow Polling at block 1542. After the CPE'spoll state has been set to a slow polling state at block 1542, the CPE'sTSP is tested at block 1550 to see if it is less than a threshold S. Ifso, then processing is done for that CPE for the present frame, and ifnot then processing advances to block 1552 where arrangements are madeso that a poll will be promptly provided to that CPE, before theprocessing proceeds to block 1500 “done.” Meanwhile, if the processingproceeded to block 1544 but the CPE did not have medium QoS connections,then the CPE's poll state may be set at block 1546. Block 1546 indicatesthat the CPE's poll state may be set to “Inactive,” at which point, forexample, individual polling may be suspended for the CPE, at least untilfurther activity occurs. The CPE may be set for only multicast polling,in which it must contend for uplink polling bandwidth provided to aplurality of such users, or even to all users which do not have otheropportunity to request bandwidth (broadcast polling). Instead ofproceeding directly to a final poll state 1546 after failing the testblock 1544, the steps of FIG. 15 may be extended in a similar fashion asblocks 1530, 1534, etc., testing for even longer inactivity at each suchextended step. Thus, block 1546 could effectively be broken into two ormore blocks, one instructing periodic multicast polling and anotherterminating all polling so that only the global contention slot remainsavailable to the particular CPE for requesting bandwidth. Other similarvariations are also possible. At the end of such poll state testing, theprocessing for the particular CPE proceeds to block 1500 to wait for thenext test cycle, which is typically provided during the next frame, butmay also be delayed by an intervening frame.

In another per-user bandwidth request technique embodiment, acalculation is performed for each user periodically, such as once perframe, to determine whether or not to poll the user immediately. Pollingis thus adjusted for each user to achieve a minimum threshold of QoSrequired by the user, and to provide increases in the polling rate inthe event of uplink bandwidth availability, limited by any needs for aconsistent polling rate, or low jitter. It is convenient to determinewhether to poll in the present frame, since inputs to the system areconstantly changing, for example as connections are added, dropped, orchanged. An exemplary Boolean function to be evaluated in thisembodiment is structured as follows:

ShouldPoll=f(Tg, minQos, maxQos, U1)

In the above equation, “Tg” is the time (which may be quantified inunits uniquely appropriate for the system, such as frames) since theuser was last granted bandwidth. “MinQos” is the minimum required QoS ofthe user, expressed as a request frequency, or request opportunities persecond, and is a function of the maximum delay which the connection orconnections of the user can tolerate: minQos=f1(max delay), where “maxdelay” is the maximum delay which can be tolerated by the user (andwhich is typically determined by the least of the maximum delaytolerances for each active connection of the user). MaxDelay may beexpressed in units of frames, in which case minQos may be determined,for example, as minQos=Framerate(in frames/s)/maxDelay. MaxDelay mayalso be measured in (standard) time units, an example of which hasminQos=1/ maxDelay(in seconds). Thus, in a system with 1 millisecondframes (a framerate of 1000/second), a connection that could tolerate adelay of 100 milliseconds (=100 frames) would haveminQos=Framerate/maxDelay=(1000 frames/s)/(100 frames)=10 (requestopportunities) per second. Similarly, if maxDelay is in time units, thenminQos=1/maxDelay=1/(100 ms)=10 (request opportunities) per second.MinQos may, for example, be determined by the least delay-tolerantconnection of a user, or may be determined by the composite delaytolerances of all active users, and thus will generally change whenconnections are set up, terminated or changed.

“MaxQos” is the maximum allowed QoS of the user, also expressed asbandwidth request opportunities per second. In a simple example,maxQos=f2(minQos, Framerate), or more specifically, maxQos=greater of[(Framerate) and (minQos)]. Thus, maxQos may be truncated at a rateequal to the frame rate of the system. However, maxQos may be permittedto exceed the frame rate by permitting plural request opportunities fora single user within a frame. Such plural bandwidth requestopportunities in a frame may be employed by a user to send data as wellas an explicit bandwidth request in the uplink, despite not havingrequested bandwidth allocation in the previous frame. “Framerate” is agenerally fixed value defined by the system, though variable frame ratesystems are also possible. MaxQos, like minQos, will generally becalculated only upon a change in connection status. “U1” is the currentuplink utilization of the link shared by the user, and may be expressedas a percent (e.g., 80 indicates that the link is currently 80% full).This value will change frequently.

In the following exemplary equation, the bracketed item returns a “1” iftrue, “0” if false:

ShouldPoll=[Tg>=(Framerate/(minQos−(maxQoS−minQoS)*(100−U1)/100))]

In the simplest case, if ShouldPoll is true, then the user for whichShouldPoll has been calculated will be immediately polled (e.g., byproviding a unit of uplink bandwidth to the user in the next uplinkmap). Evaluating the above equation each frame for a user yields apolling determination for such user on a substantially continuous basis,based upon characteristics of the user (e.g., minQos, maxQos, and Tg)and upon characteristics of the link shared by the user (e.g.,Framerate, U1). The basis of the exemplary “ShouldPoll” equation, issubstantially, but not absolutely, continuous. Its absolute continuityis limited by system quantization due, for example, to the integralnature of frame units which limit the continuity of expressedfrequencies (frames per second) and of time (when it is expressed inframe periods between events). An equation based upon a combination ofone or more variables which are allowed to take on all applicablevalues, limited only by the applicable range and quantization level ofthe variables, has a substantially continuous basis. An equation whichcombines one or more variables to form a compound variable which cantake on a large number (generally, more than a dozen) of possible valuesalso has a substantially continuous basis. Note that when implementingfunctions such as the exemplary equations above, it may be convenient tomodify the equations to use values inverse to QoS (which is typically inunits of request opportunities per second). For example, one may useminPollPeriod=1/maxQos, and maxPollPeriod=1/minQos. Since minPollPeriodand maxPollPeriod are inverse to QoS frequency values, they may beexpressed as time, for example in units of frame periods. Based upon theforegoing explanation and examples, the skilled person can readilyderive alternative continuous functions based upon the particular needsof the system with which they are working.

The preceding examples explicitly teach per-user adaptation, as distinctfrom “group-based” adaptive techniques for obtaining bandwidth requests.However, group-based and per-user techniques are not mutually exclusive,and practical systems will often employ aspects of both group-based andper-user adaptation techniques. In a single exemplary system, some usersmay be polled based upon substantially continuous functions ofparameters uniquely associated with them (with or without otherparameters common to the channel), while other users are polledaccording to a rate established for a group, or polling category, ofwhich they are a member. For example, users falling within one arbitraryrange of activity may be designated for group polling, while userswithin another arbitrary range of activity are designated for zeropolling; yet users falling outside those two ranges may be polled on thebasis of a substantially continuous function of relevant parameters. Alllogically consistent combinations of group-based and per-user techniquessuch as taught herein are embodiments which may be appropriate for somesystems, and may be selected for a particular system based uponengineering considerations of performance and convenience.

Users, Groups and Categories

The foregoing principles teach obtaining bandwidth requests from usersadaptively based upon parameters of the users, or upon compositeparameters of a group of users. The users, and groups and categories ofusers, which exist in different embodiments, may vary substantially incharacter. In general, a user is an identifiable entity communicatingvia a base station and having at least one communication parameter(relevant to obtaining uplink bandwidth) which reflects the user'scommunication via the base station. The user is treated as a discreteentity for purposes of obtaining BW, and is granted BW as a unit. Userscan be an individual connection, a plurality of logically groupedconnections, or physically grouped connections. All of the connectionsserved by a particular CPE, and logical subgroups of connections withina CPE, are examples of grouped connections forming a user which istreated as a single entity for BW allocation purposes. Subgroup userswithin a CPE may be based on common conditions, such as common QoS, ormay be organized as a “user” based on load-sharing principles.

Above, a group of distinguishable entities is described as beingtreatable as a discrete user for purposes of bandwidth requests andallocation. However, a group of such discrete users may be treated incommon in some regard. For example, one group of CPE users might bedefined by the fact that they communicate by a common shared channel(common frequency and transmitter), have common modulation and forwarderror correction (FEC) settings, and further have low recent BW usage.Such a group of CPEs can, for example, be given the same multicastpolling opportunities. However, this is a group of discrete users, andthus each user may request BW, and have BW allocated, on an individualbasis. Membership in such a group is, in general, variable dependingupon relevant conditions.

A plurality of users may be defined as belonging to a category of users,such as those users sharing the same physical connection channel andhaving a particular QoS, or those users sharing the same physicalconnection, modulation level and FEC technique. Decisions regarding BWallocation may be based in part upon one or more such categories towhich a particular user may belong.

Communication parameters may also be categorized, which is to say that arange of a particular parameter may be treated the same for somepurpose. For example, users may be identified as belonging to aparticular category of users which share the same physical connectionchannel and also have a particular category of recent BW usage. Thus,users sharing the same physical channel may be identified as belongingto a “low usage,” a “recently active,” or an “active usage” category inregard to the value of this parameter which is applied to them. In thisway, a parameter such as “time since BW last allocated” may be treatedas having a finite of possible states, as an alternative to beingtreated as a practically continuous variable parameter.

These possibilities, for BW request and allocation purposes, ofdesignating a group of identifiable entities as a single user, ofdesignating a category of users for common treatment in some respect,and of responding to communication parameter value either as a member ofa category of such values, or as a continuously variable parameter, adda large measure of flexibility to the inventive BW request andallocation techniques taught herein. Each claim must be interpreted,insofar as possible, as referring to all such alternativeinterpretations. Moreover, the foregoing examples may provide somespecific meanings for the terms “user,” “group” and “category,” but allsuch specific meanings are in addition to the usual dictionary meaningof the terms, rather than limitations on the dictionary meanings.

Adaptive Bandwidth Request Technique Modules

A system using the above bandwidth request processing techniques mayimplement them within a series of functional modules. For example, theinformation flow diagram of FIG. 16 reflects a system having a pollingpolicy module 1610, an individual poll module 1620, a bandwidth requestprocessing module 1630, a “poll-me” message processing module 1640, amulticast poll module 1650 and associated contention resolution module1660, and a channel bandwidth allocation module 1670. These may befunctional subsections of an overall base station LL-MAA MAC 1690 forcontrolling access to one physical channel.

The polling policy module 1610 may be a functional block within a basestation LL-MAA MAC handling a particular channel. The polling policymodule will be configured to adaptively control the technique by whichbandwidth requests will be obtained from each user. The configurationmay employ any combination of the adaptive techniques described above,for example as shown in FIGS. 14 and 15, and in particular may employany combination of polling group-based and per-user calculations tochange the technique or rate at which opportunities for solicitingbandwidth are provided to each particular user. Thus, for example, thepolling policy module may establish zero polling for currently activeusers, may assign users having a range of usage history and QoS needsand guarantees to one or more polling groups to which multicast pollsare made on a bandwidth-available basis, and may individually poll usersat a periodic rate depending substantially on per-user communicationparameters, such as recent bandwidth usage, physical connection QoS,number of active connections (for users which are groups or CPEs), andcontractual QoS. In the less complex organization, as shown, the uplinksubframe map queues, the “poll-me” message processing module, and thebandwidth request processing module each provide inputs to the pollingpolicy module. Other inputs (not shown) are provided from higher levelsof the system to indicate contractual QoS, user groups and connectionIDs. However, more complex structures may include other datainteractions, such as direct interactions between the polling policymodule and the channel bandwidth allocation module, to permit balancingbetween these independently adaptive systems before the channelbandwidth allocation module directs the allocation in the uplinksubframe map queues. The polling policy module may be a functional blockof the base station LL-MAA MAC. It may be implemented at least partly insoftware, but the skilled person will understand that engineeringconsiderations may indicate an advantage of having some or all of thefunctions of this module performed in hardware, such as in one or moreASICs.

The individual poll module 1620 may be configured to prepare forindividual poll of one or more target users and to queue such a poll forthe next available downlink to the CPE handling (or identical to) eachuser. The individual poll module may accept instructions from thepolling policy module defining which users to individually poll, and arate or a priority for such polling, and may provide detailed pollingbandwidth instructions to the channel bandwidth allocation module 1670.This module may also accept poll instructions from the “poll-me” messageprocessing module 1640. The individual poll module may be a functionalblock within a base station LL-MAA 1690 handling a particularcommunication channel, and may be implemented in hardware, in software,or more typically in a combination of both, based upon engineeringconsiderations such as the structure of associated modules.

The bandwidth request processing module 1630 may be configured toidentify bandwidth requests disposed in the uplink communicationsreceived from the CPEs, and to interpret such requests. The module 1630generally receives data from the base station LL-MAA MAC uplinksub-frame map queues 1680 identifying polling slots, and particularlycontention slots, in the uplink sub-frame map. This information may becompared with the demodulated data actually received on the uplinkreceive queue 1690. An analysis of the data received during contentionslots may readily be devised by the skilled person, for the particularprotocol of the system, to distinguish a probable collision from a validbandwidth request, and also from an absence of any response. Informationindicating a probable collision may be forwarded to a contentionresolution module 1660, described below. The bandwidth requestprocessing module 1630 may be a functional part of the base stationLL-MAA MAC 1690, and like other modules of the base station LL-MAA MAC,may be implemented in any combination of software and hardware. Theoutput from the bandwidth request processing module, requests forbandwidth, may be directed to the channel bandwidth allocation module1670.

The “poll-me” message processing module 1640 may be configured tointerpret the poll-me message (and similar messages, such as a prioritypoll-me message, if used) to cause an active CPE to be polledindividually. The “poll-me bit” processing module receives as an inputthe data in which may contain a “poll-me” message, identifies thatmessage, and appropriately requests polling bandwidth from the channelbandwidth allocation module 1670.

The multicast poll module 1650 may be configured to identify, forexample by input from the polling policy module, which CPEs are eligiblefor multicast polling due to their relatively low probability ofrequesting bandwidth. The multicast poll module 1650 may examine thepreviously identified polling groups which have been assigned, and maybalance individual request probability for each member in such groupswith the group size to determine a preferred multicast polling rate forthe group. The multicast polling bandwidth output from this module maybe directed to the channel bandwidth allocation module 1670. This modulemay be implemented in any practical combination of hardware andsoftware.

Since multicast polling provides a potential for contention, anassociated contention resolution module 1660 may perform the stepsdescribed previously to resolve collisions. The contention resolutionmodule 1660 may receive information from the bandwidth requestprocessing module 1630 indicating probable collision and potentiallyinvolved users (e.g. those polled during the contention slot which didnot receive a separate individual poll nor dispose a poll elsewhere inthe received uplink queue). The contention resolution module 1660 maythen select a contention resolution procedure depending upon thecircumstances, and may indicate to the channel bandwidth allocationmodule 1670 when further individual or multicast polls should beprovided to members of the contending group.

The channel bandwidth allocation module 1670 may receive inputs from thebandwidth request processing module 1630, the individual poll module1620, and the multicast poll module 1650, and then direct thedisposition of each bandwidth slot to the base station LL-MAA MAC uplinksub-frame map queues 1680. The bandwidth request processing module maytake into account the available bandwidth of the channel, and mayimplement fairness algorithms (described elsewhere) to balance thebandwidth requests and availability, thus providing adaptation in thegranting of uplink bandwidth. Such grant adaptation interacts with thedistinct function of adaptively obtaining bandwidth requests, since theamount of bandwidth granted affects the bandwidth available for polling,as well as affecting the communication parameters of each user.Accordingly, a variation not shown in FIG. 16 permits direct interactionbetween the channel bandwidth allocation module 1670 and the pollingpolicy module 1610 to permit iterative solution of the polling policyand bandwidth allocation adaptations.

Each of the modules described above may perform its data manipulationsin a processor under software or firmware control, or in hardwarespecifically prepared for the tasks, or in a combination of hardware andsoftware. Moreover, those skilled in the art will understand thatfunctions which are described as being performed by certain systemmodules may in general be performed by different modules. FIG. 16 showexemplary information flows, but many other information flows arepossible in various embodiments of a system having a base station whichadaptively obtains bandwidth requests from users.

SUMMARY

In summary, the bandwidth allocation method and apparatus describedherein includes powerful, highly efficient means for allocatingbandwidth in a broadband wireless communication system. The presentbandwidth allocation method and apparatus uses a combination ofindividual and group polling techniques, contention-based polling,piggybacking, and CPE-initiated techniques to efficiently allocatebandwidth in a communication system. These may be employed withparticular efficiency by dynamically and adaptively categorizing CPEsinto polling groups, and using the bandwidth allocation techniques mostappropriate for each such group. Advantageously, only those currentlyactive CPEs (CPEs that currently have bandwidth allocations associatedthereto) are permitted to request more bandwidth using either thepiggybacking or poll-me bit methods. In addition, a base station cansave bandwidth by implicitly informing the CPE of additional bandwidthallocation. The base station implicitly informs the CPE of additionalbandwidth allocation by allocating additional bandwidth to the CPE inthe uplink sub-frame map. Similarly, the base stations implicitly pollthe CPEs by allocating bandwidth in the uplink to enable the CPEs torespond to the poll with a bandwidth request.

In honoring the bandwidth requests, the base station builds andmaintains a logical queue of the data to be transmitted. The queues aredeveloped by the base stations based upon the QoS. In addition, the basestation allocates bandwidth based on a combination of QoS and a QoSunique fairness algorithm. The CPE itself, rather than the base station,distributes the allocated bandwidth to its services in any manner theCPE determines to be appropriate. Thus, the CPE can use its allocatedbandwidth in a manner that differs from the originally intended (andrequested) purpose.

A number of embodiments of the present invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the scope of the invention. Any DAMA systemmay efficiently obtain and react to varying bandwidth needs by employingthe adaptive techniques described herein. The method and apparatusdescribed herein can be used in many types of data communicationssystems, such as a satellite communication system. In such acommunication system, satellites replace the base stations describedabove. In this case, the CPEs may not be at fixed distances from thesatellites, making more difficult to schedule DAMA services for theCPEs. The methods described herein are not limited to wireless systems,but can be used in a wired communication system. The only differencebetween some wired systems and the wireless system described above isthat the channel characteristics vary between the two. However, thebandwidth allocations do not change as between the two types of systems.

Other systems, both wired and wireless, may share media between aplurality of users without using frames as they are described herein.Even in such systems a scheduling interval for allocating opportunitiesto request bandwidth may be dynamically varied in accordance with theteaching herein in order to efficiently determine user bandwidth needs.Accordingly, it is to be understood that the scope of the invention isnot to be limited by the specific illustrated embodiments, but only bythe scope of the appended claims.

1. A subscriber station for a broadband wireless communication systemcomprising: a transceiver; and a Media Access Control (MAC) moduleconfigured to provision a bandwidth request specifying a requestedamount of uplink (UL) bandwidth pertaining to a connection establishedat the subscriber station, receive a UL bandwidth grant for theconnection, and allocate the UL bandwidth grant to at least one of aplurality of connections established at the subscriber station.
 2. Asubscriber station as claimed in claim 1, wherein the MAC module isfurther configured to identify the UL bandwidth grant.
 3. A subscriberstation as claimed in claim 1, wherein the UL bandwidth grant isspecified in a UL frame map received by the subscriber station.
 4. Asubscriber station as claimed in claim 2, wherein the UL bandwidth grantis specified in a UL frame map received by the subscriber station.
 5. Asubscriber station as claimed in claim 1, wherein the UL bandwidth grantis based on a type of service established for the specified connection.6. A subscriber station as claimed in claim 1, wherein the UL bandwidthgrant is based on a respective communication parameter associated withthe subscriber station.
 7. A subscriber station as claimed in claim 6,wherein the communication parameter includes the quality of servicerequired by at least one of a plurality of user connections served bythe subscriber station.
 8. A subscriber station as claimed in claim 6,wherein the communication parameter further includes the amount ofbandwidth available for sharing among the subscriber stations.
 9. Asubscriber station as claimed in claim 6, wherein the communicationparameter further includes the number of active subscriber stations. 10.A subscriber station as claimed in claim 6, wherein the communicationparameter further includes the bandwidth currently used by downlink (DL)traffic.
 11. A subscriber station as claimed in claim 6, wherein thecommunication parameter further includes a composite priority parameter.12. A subscriber station as claimed in claim 6, wherein thecommunication parameter further includes an estimated amount ofbandwidth needed to accommodate bandwidth requests.
 13. A subscriberstation as claimed in claim 1, wherein the UL bandwidth grant isallocated between connections based on a type of service established foreach connection.
 14. A subscriber station as claimed in claim 1, whereinthe UL bandwidth grant is allocated based on the current state of queuesassociated with the plurality of connections.
 15. A subscriber stationfor a broadband wireless communication system comprising: transmit andreceive circuitry; and a Media Access Control (MAC) module configured totransmit an explicit message requesting a polling opportunity forenabling the subscriber station to request uplink (UL) bandwidth,receive a polling opportunity as a given amount of UL bandwidth, andprovision a bandwidth request within the given amount of UL bandwidth,the bandwidth request specifying a requested amount of UL bandwidthpertaining to a specified connection established at the subscriberstation.
 16. A subscriber station as claimed in claim 15, wherein theMAC module is further configured to receive a UL bandwidth grantidentified in a UL frame map.
 17. A subscriber station as claimed inclaim 15, wherein the explicit message is a poll-me message.
 18. Asubscriber station as claimed in claim 17, wherein the poll-me messageis a poll-me bit provided in a reserved field in the header of a packet.19. A subscriber station as claimed in claim 17, wherein the poll-memessage is a particular combination of bits provided in a reserved fieldof a packet.
 20. A subscriber station as claimed in claim 17, whereinthe poll-me message specifies the required amount of bandwidth inbandwidth units.
 21. A subscriber station as claimed in claim 17,wherein the poll-me message further identifies an additional bandwidthrequest message within the UL traffic.
 22. A subscriber station asclaimed in claim 15, wherein the MAC module is further configured toinsert the bandwidth request within bandwidth already allocated to ULtraffic.
 23. A subscriber station as claimed in claim 15, wherein thebandwidth request has a specified structure for identification by areceiver.